with a pair of oblong and pointed labial palps. Branchiæ | the spot where it begins to lean upon the adductor muscle in form of a crescent, and formed of detached filaments. this ventricle is flattened and lobated on each side; the Foot rudimentary, on the disk of which a club-shaped pedi- auricles are similar, equal, and symmetrical; they are a cle raises itself. Anus floating behind the adductor muscle little elongated, pyriform, and their extremity is continued of the valves. (Deshayes.) into a great branchial vessel, which soon becomes bifurcate. The distribution of the vascular system exhibits nothing particular, and resembles that of the Pectens and other acephalous mollusks. Shell inequivalve, adherent, auriculated, beset with spines or rough; the umbones unequal; the lower valve offering an external cardinal facet which is flattened and divided by a furrow, and which increases with age. Hinge with two strong teeth in each valve, and an intermediate fosset for the ligament, communicating by its base with the external furrow. Ligament internal, the antient remains of which show themselves externally in the furrow. (Lamarck.) Spondylus ducalis: internal view of valves, showing hinge, ligament, mnscular impression, &c. a. upper valve; b, lower valve. M. Deshayes remarks that there are few genera better characterized than Spondylus; so that, known as it has been from the days of Rondeletius and other naturalists of the same epoch, he has nothing to add to what Lamarck says of the shells; but, he adds, that as Lamarck gives an insufficient account of the animal, he will supply it. M. Deshayes describes the animal of Spondylus as rounded or oval; its thickness being variable in different species. As in all the mollusks of the same family, the two lobes of the mantle are disunited, except in the short extent of the dorsal border corresponding to the hinge; they are thick in their circumference, and furnished with many rows of rather long fleshy cilia, between which, and on the internal border, may be remarked a certain number at irregular distances, truncated in the middle, and terminated by a smooth and convex surface, recalling to the mind of the observer the ocular surface of the tentacula of certain mollusks. [CONCHIFERA, vol. vii., p. 433.] These peculiar organs, he remarks, are also seen in Pecten and Pedum. He describes the adductor muscle as very large, circular, placed in the median and posterior part of the animal, and easily divided into two unequal parts. The abdominal mass is placed round this muscle, and especially at its anterior side. The mouth is situated below the anterior commissure of the mantle, it is surrounded with a large slashed lip, fringed on the edge and accompanied on each side with a pair of palps, but little elongated, in the form of myrtle leaves. The mouth communicates with the stomach by a sbort and rather wide esophagus. The stomach is elongated, pyriform, conical, and continues itself by its pointed extremity into a cylindrical and slender intestine; this makes a single great convolution in the thickness of the liver, or rather, a great ansa having the sides parallel. It mounts again towards the dorsal border between the stomach and the adductor muscle, gives support to the ventricle of the neart, leans immediately afterwards on the superior and posterior surface of the muscle, and turns on itself to terminate posteriorly in a floating anus, which is easily perceptible in the posterior commissure of the mantle. At the anterior part of the animal, and towards the middle of the abdominal mass, a singular organ is found; it is composed of a disc supported by a short pedicle; from the centre of this disc a small cylindrical tendon, terminated by a small oviform fleshy mass, elevates itself. We see, remarks M. Deshayes, in this peculiar apparatus, a modification of the locomotive organ, the foot, become here useless for changing the place of the animal, because it invariably and immediately fixes its shell on rocks or other solid bodies constantly bathed by the sea. The branchia resemble those of the Pectens; they are large, equal, and crescent-shaped. The heart is symmetrical; a single ventricle embraces the intestine at We would add to the account above given of the shell of this genus, a few observations which we have made, sufficiently obvious indeed, but which have not, as far as we are aware, been noticed. The spines with which the Spondyli are armed, in some instances very long, must have struck everybody, and also that they bristle out on every side from the upper valve. The lower valve is attached, and adheres to submerged bodies by means of foliations. If the whole lower surface adheres, as it often does, not a spine is given out from the lower valve; but where the adhesion takes effect towards the anterior part of the lower valve only, as is very frequently the case, especially when the shell is affixed among the branches of corals, a favourite locality with some species, the foliations are confined merely 10 that part where adhesion is required, and the rest, or free part of the valve, is as profuse of spines as the upper valve itself. There are two points to be gained, support or adhesion, and defence; the first is of primary importance, but as soon as that is safe, all the resources of the animal seem to be turned towards its defensive and offensive armour. Those fishes which browse among the corals are thus deterred from injuring the living fixture which has there taken up its abode. A very fine series of specimens was collected with a view to this habit, and they showed not only the power which the animal had of secreting the proper process of shell according to the circumstances required, but of modifying the secretion according to the exigencies of the occasion. Spondylus Americanus, with the valves closed; the umbones towards the spectator. But there is another, and more interesting phenomenon, well displayed in one of the species of this genus. Professor Owen, having been led to reflect, while considering the uses of the camerated part of the shell of NAUTILUS, upon the degree or extent of that structure as possibly dependent upon the mode of growth of the animal and its shell, and how far it was a necessary physical consequence of the increase and change of position of the animal, independently of any special purpose served by the forsaken parts or chambers of the shell, had paid attention to all the cases that had come under his observation of the formation of chambers in shells, by the secretion, on the part of the animal, of a nacreous layer, forming a new basis of support to the soft parts, and cutting off the deserted portion of the shell from the chamber of occupation. He laid the following observations on the structure of the Water-clam (Spondylus varius, Brod.) before a meeting of the Zoological Society of London, in June, 1837, and he observes that it is well known that the prosess above adverted to is not the only mode adopted to suit the shell to the changing form and bulk, or other exigencies of its occupant. Taking the genus MAGILUS, for one example, the Professor remarks that the part of the shell from which the body gradually recedes is filled up by the continuous compact accretion of calcareous matter, and a solid massive elongated shell is thus produced, which would be a great incumbrance to a locomotive mollusk, but is of no inconvenience to a univalve SPO 373 Again, in Helix decollata, he observes, the deserted part of the shell, after being partitioned off by the nacreous layer secreted by the posterior part of the mantle, is broken away by some yet unexplained process, and, consequently, no chamber nor any solid apex of the shell remains. destined by nature to live buried in a mass of lithophytous | but to the preceding and succeeding septum at the part occupied by the adductor muscle, and for an extent correThe progressive change in coral. sponding to its circumference. the position of this muscle by the absorption of the posterior fibres and the addition of others anteriorly, changes in a corresponding degree the relative position of these subcentral confluent parts of the septa, and a beautiful undulated disposition of the whole chambered part is the result. If the adductor muscle were a tube instead of a solid mass, the central confluent part of the septa would of course be perforated, and a siphon would result, the calcareous walls of which, from the proximity of the chambers, would no doubt be continuous, as in many Polythalamous shells. The same author notices the disposition to form chambers manifested, but in a much less degree, in the smaller flattened or superior valve of the species under consideration. In the specimen which formed the subject of his paper there were three chambers, with narrower intervals and much thicker partitions than in the lower valve. These partitions were confluent opposite to the muscular impression, as in the lower valve, and each partition expanded from this attachment in an infundibular manner, which reminds the observer of the emboitement of the calcareous part of the siphon in the Spirula. But, continues the Professor, the retention of the deserted chambers, and the interception of certain spaces of the shell by calcareous septa, though not unknown in the gastropodous univalves, is more common in bivalves; and he adduces the case of a common oyster, which, if kept without food, will frequently expend its last energies in secreting a new nacreous layer, at a distance from the old internal surface of the concave valve, corresponding to the diminution of bulk which it has experienced during its fast, and thus adapt its inflexible outward case to its shrunken body. Then he instances the calcareous tube exuded from the elongated mantle of Lamarck's Septaria, in which the closed extremity is divided into chambers by a succession of layers at a distance of half an inch from each other, having a regular concavity towards the open extremity of the shell. These concave septa are, he observes, composed entirely of the nacreous constituent of the shell: in one specimen which he examined they were six in number; and he adds that they are thin, smooth, and closely resembling the partitions in the NAUTILUS and SPIRULA, save in the absence of the siphonic perforation. Returning to the bivalves, Professor Owen points out the fact that among them the Ostreæ not unfrequently present shallow and irregular chambers in the substance of the shell, and that the Etheria have vesicular cavities interposed between the testaceous lamina; but he states that the most constant and remarkable example of the camerated structure of the shell is presented by the large Spondylus or Water-Clam above named, so called from the fluid which (until lost by slow evaporation) occupies the chambers, and which is visible in the last-formed chamber through the thin semi-transparent exposed septum. 'The secreting power of the lower lobe of the mantle in the Spondylus,' says Professor Owen in continuation, is greater than in the upper; and the layers of nacre which are successively deposited on the cardinal margin push forward in a corresponding degree the upper valve, leaving a heel or umbo behind the hinge of the lower valve, which, from the inactivity of the secreting surface of the upper lobe of the mantle, is not opposed by a corresponding umbo in the upper valve. 'The lamina, which are deposited in a continuous series of superimposed layers at the hinge of the lower valve, are not continued in a like state of superposition throughout; they soon separate from each other, and do not again unite, except at the space corresponding to the adductor muscle, and at the circumference of the valve. The interspaces of these succcessive layers of the growWe possessed several fine examples of this species, and it was only in advanced stages of growth that the watering Spondylus cannot, from the absence of a medium of was included. Young shells were entirely without it. The intercommunication, serve any purpose hydrostatically with reference to locomotion: it is a singular fact indeed that the old shells, some of which were of great size, were copiously supplied. The water could be seen through the semi-Spondylus, in which the chambered structure is constant, transparent floor or septum on which the animal reposed in the lower valve, and through the thin ceiling, so to speak, As the shell was turned in the hand, of the upper valve. the fluid could be observed through these transparent laminæ finding its level with air-bubbles at its surface, and could be heard as it trickled to that level. But to return to the Professor's interesting memoir. In order to examine this camerated structure, and more especially to see how it was modified by the presence and progressive change of place of the adductor muscle, he had a fine specimen sawn through vertically and lengthwise: it measured eight inches in length; the substance of the concave valve, which was two inches and one-third in thickness at the thickest part, included fourteen chambers, separated from each other by very regularly formed and stout partitions, composed, as in other chambered shells, of the nacreous portion or constituent of the shell.. The septa were slightly undulating in their course, but presented a general concavity towards the outlet of the shell. Not any of these partitions were however continued freely across the shell, but each became continuous at the muscular impression, which is near the middle of the shell, with the contiguous septa. In general also the septa commenced singly from the cardinal or upper wall of the valve, and divided into two when about one-fourth of the way towards the opposite or lower wall; the thickness of the undivided part of the septum being equal to, or greater than, that of the two divisions of layers into which it splits. Professor Owen accounts for the fact of the septa becoming united together at the point of insertion of the adductor as follows:-The muscle never quits its attachment to the valves; while the lobe of the mantle, except in its circumference, and where it is attached to the adductor muscle, must detach itself from the surface of the valve which is about to be partitioned off, when it secretes upon the interposed fluid the new septum or basis of support. It is obvious therefore, he observes, from the condition under which the partitions are successively secreted, that they must adhere not only to the circumference of the valve, and the Ostree and other bivalves, in which it is occasional, are cemented to extraneous bodies by the outer surface of the shell, generally by the concave valve. So that the septa must be regarded as mere dermal exuvia still left adhering to the animal, to which, as a motionless bivalve, they are no incumbrance. It is highly probable that all the chambers are originally filled with fluid, as more or less is found in the outer ones of the specimens brought to this country. 'In the Testaceous Cephalopods a new structure is added, viz. the siphon, whereby the exuvial layers of the old shell and the deserted chambers are converted into a hydrostatic instrument, subservient to the locomotion of the animal. The operation of the siphon and chambers has been ably explained by Dr. Buckland in the Nautilus, where the calcareous inflexible tube protecting the membranous siphon is not continuous. The working of the siphon is however less intelligible in those species in which the outer calcareous tube is continued from chamber to chamber, as in the Spiruia, Orthoceratites, &c.; and it is with respect to camerated shells of this kind that I would ask how far the reasoning suggested by the chambers in the Water Spondylus may be applicable in their case, and whether a final intention can be clearly traced beyond the diminution of specific gravity occasioned by a large proportion of the shell being converted into receptacles of gas; if indeed we have sufficient evidence to assume that they do not contain a denser fluid, like the Spondylus.' The cut represents a section of a very old individual of this species, in which the upper valve was very convex, and furnished with a great number of septa. The fluid contained in the specimen exhibited by Mr. Owen, which is in the Museum of the College of Surgeons in London, was put into the hands of Dr. Bostock for examination by him, and the Doctor obtained the following results:— It was turbid, had an acid saline taste, and a rank disagreeable odour. After standing for twenty-four hours, it The clear fluid, amounting to 54 m., was deposited a whitish curdy sediment, and became clear and transparent. Section of Water-Spondylus cut longitudinally through both valves, which are represented as closed. no effect. poured from the sediment, and was subjected to various tests. It was neither acid nor alkaline; it produced a very copious precipitate with the nitrate of silver, indicating the presence of a large proportion of muriatic acid; the muriate of barytes indicated a slight trace of sulphuric acid; while the appropriate tests of lime, magnesia, and iodine produced A portion of the fluid was evaporated by a gentle heat, when a quantity of crystals of the muriate of soda was obtained, amounting in weight to very nearly twenty per cent. of the fluid. After the removal of the crystals, a little brown matter was left in the capsule, but in too minute a quantity to enable Dr. Bostock to ascertain its nature and properties, except that it was not soluble in alcohol: we may however, he observes, presume that it gave the fluid its peculiar flavour and odour. It appeared then that the fluid in question consisted almost entirely of a solution of pure muriate of soda, differing therefore in its chemical constitution from sea-water. The sediment above mentioned appeared to consist of small globular, or rather, pyriform bodies, probably of an organic origin. (Zool. Proc.) Geographical Distribution, &c. of the Genus.-Spondylus has been found attached to rocks, corals, other shells, &c., at depths varying from the surface to seventeen fathoms in the seas of warm and temperate climates (the Mediterranean for instance). The finest and most beautiful species are natives of tropical and intertropical localities. The number of recent species recorded by M. Deshayes in his tables is 25. Of these, Sp. gæderopus is noted as recent and fossil (tertiary). The number given in the last edition of Lamarck is 21; but this does not include Spondylus varius, nor four other species brought home by Mr. Cuming, and described by Mr. Broderip. (Zool. Proc., Synopsis Testaceorum.) Plicatula. Scania and Maestricht, and the second (Plagiostoma spinosum, Sow. from that of England, Gerinany, and France. The number of fossil species of Plicatula noted by M. Desliayes as being found in the tertiary beds is seven. In the last edition of Lamarck the number recorded is ten: the locality given to one there described (Plicatula pectinoides) is the lias of France, Germany, and England. Mr. Lea notices another (Plicatula Mantellii) from the Claiborne beds (tertiary). Dr. Mantell records two (Plicatulæ inflata and pectinodes) from the chalk-marl, Sussex. Dr. Fitton notes the same two species from the gault and lower green-sand, and an uncertain species from the Portland stone (Dorset, Bucks), and the Oxford oolite (Cam.). Professor Sedgwick and Mr. Murchison record Plicatuia asperu from the Gosau deposits, and its equivalents in the Aips. Of the other so-called genera belonging to this family, Dr. Mantell gives Plugiostomata spinosum, Hoperi, and Brightoniense, as found in the Sussex chalk-formation, and Dianchore luta and obliqua, from the same locality; Plagiostomata elongatum and asperum from the chalk-marl, and an unnamed Plagiostoma from the firestone or upper green-sand. Mr. Lonsdale enumerates Plagiostomata giganteum, punctatum, duplicatum, and Hermanni, from the Bath lias, and unnamed Plagiostomata from the inferior oolite, the great oolite, and the Forest marble of the same district; that from the Forest marble with a? Professor Phillips records Plagiostoma giganteum, from the inferior oolite and lias; Pl. rusticum, from the lias and coralline oolite; pectinoïdium, from the upper lias; læviusculum and rigidum, from the coralline oolite; rigidulum, from the cornbrash; one from the Oxford clay; cardiforme? one from the Bath oolite; duplicatum, from the coralline oolite, Oxford clay, and Kelloway's rock; and interstinctum, from the cornbrash and Bath oolite. Also Dianchora striata, from the chalk. (Organic Remains, Yorkshire Coast.) Dr. Fitton's list includes Plagiostomata cardiiforme, elongatum, Hoperi 2 rigidum, obliquatum, rusticum, and a small species; and Podopsis striatus (Dianchora striata). (Strata below the Chalk.) The number of Plagiostomata given in the last edition of Lamarck, exclusive of Pl. spinosum, noticed above, is six. The number of Podopsides stated in the same work, exclusive of Pod. truncata, noticed above, is one, viz. Podopsis gryphoides, and M. Deshayes expresses his opinion that Lamarck founded this species on a variety of Ostrea vesicu laris; at all events, he says, M. Goldfuss is wrong when he refers this shell to Brocchi's Ostrea navicularis; this species, he adds, peculiar to the Subapennine beds, has never been found at Meudon. SPONDY'LUS. [SPONDYLIDE.] SPO'NGIA, the generic name under which Linnæus and many subsequent systematists have ranked the very numerous forms of organization analogous to the sponges of commerce. Generally, and we think justly, zoologists have claimed these organizations for the animal kingdom, and ranked them among the zoophyta; but there are eminent writers who dissent from this view on different grounds, and prefer to rank the marine and freshwater sponges with plants. That the animal and vegetable organizations both terminate obscurely toward the inorganic structures of creation, and that in this approach to their common boundary they touch and melt into each other at more than one point, are propositions which, for the purpose of the present argument, and in the actual condition of natural history, seem to require no proof; but much of the difficulty which is admitted or supposed to attend an exact determination of the animal or vegetable nature of certain stony corals (Nullipora, Lamarck), Spongiada, Corallinadæ, &c. arises from a want of recollection and application of these truths. If the boundaries between the animal and vegetable creations be inde finite, this must happen because the structures and funetions to which these terms are rightly applied insensibly pass into and mix with each other, so as to render definition impracticable by single diagnostic characteristics, and difficult even by a careful summation of analogies and differences. When therefore zoologists define animal life to be characterized by locomotion, by sensation, or by irritability; or by a certain chemical constitution; or by certain orders of structures, as an internal digestive cavity, a nervous system, and the like,-it is not to be wondered that whole groups of undoubted animals are excluded by this inadequate method from all place in the real system of nature, and thrown into an appendix. But if, on the other hand, we recognise and act upon the principle that life manifests itself on the globe in a variety of aspects no otherwise limited than by certain general conditions, and by special adaptation to peculiar exigencies, then it will follow that all organic structures will be grouped round particular types, according to the number and importance of their agreements; these types, treated as single objects, will admit of similar arrangements; and a general classification may result, approaching to a really natural system,' and justifiable on the basis of the inductive philosophy.' [SARCOIDEA.] The pervading idea which connects together the members of each group round one central type, is a community of structure and functions, and the place of a group among the other types of animal or vegetable life will be found by the analogies which, in respect of these structures and functions, it presents with other groups. transparent globules, connects the different parts of the Horny sponges with anastomosing fibres, fit for domestic use, belong mostly to warm zones of the sea; sponges with calcareous spicula are rather numerous on the British coasts; and siliceous spicula are common in the sponges of most latitudes. [SPONGIADE.] Remains of both horny and spicular sponges occur in a fossil state. Considered in this manner, sponges, though they may not, as Aristotle reports, ever exhibit a shrinking movement (Kivno) when touched-though no polypi and no real digestive cavities are recognised in them, must surely be admitted among the zoophyta. For in regard to their constituent structure, they are composed, as so many of the Polypiaria are, of a firm horny or stony skeleton, immersed in a soft gelatinous living mass; in respect of the aspect of these two substances, the resemblance which they offer to Alcyonia appears very strong, while their external forms, uncommonly varied, sometimes resemble Alcyonia, often approach to Palmipora, frequently to Pavonia, Agaricia, and other forms of Lamelliferous Zoophyta. The currents of water which pass through the canals of their substance are analogous to many operations among Polypiaria and Mollusca, and perhaps depend on similar ciliary organs, though, except on the young ova of sponges, they have not yet been detected. As however they contain no Polypi, it is difficult to rank them under the Polypiaria. Dr. Johnson omits, in his excellent work on British Zoophyta, the sponges, and the following summary of his reasons deserves attention: If they are not the productions of Polypes, the zoologist who retains them in his province must contend that they are individually animals, an opinion to which I cannot assent, SPO'NGIA, MEDICAL USES OF. The use of sponge seeing that they have no animal structure or individual by surgeons, in its natural state, to absorb fluids, needs no organs, and exhibit no one function usually supposed to be notice, but it is also employed by them under the name of characteristic of the animal kingdom. Like vegetables, they sponge tent, when prepared in a particular manner. This are permanently fixed; like vegetables, they are non-irri- consists in dipping the sponge in melted wax, and comtable; their movements, like those of vegetables, are extrinsi-pressing it between iron plates till it hardens on cooling; it cal and involuntary; their nutriment is elaborated in no appropriated digestive sac; and, like cryptogamous vegetables or algae, they usually grow and ramify in forms determined by local circumstances, and if they present some peculiarities in the mode of the imbibition of their food, and in their secretions, yet even in these they evince a nearer affinity to plants than to any animal whatever.' On this we may remark, that very many animals are as permanently fixed as sponges; that irritability is not to be looked for in every part of a sponge, any more than in a Rhizostoma, whose divided digestive cavities are very unlike ordinary stomachs; and that the forms of sponges include remarkable analogies with the supports of Polypi. It is to our countrymen Ellis and Dr. Grant that the history of sponges is most indebted. The former established the existence and nature of the currents of water which pass through the substance; and the latter, besides confirming the results of Ellis, added a vast quantity of new and valuable observations. Mr. Bowerbank has contributed precise ́nformation regarding both the fossil and recent sponges. Ellis, On Corallines; Grant, On Sponges,' in Edinburgh Phil. Journal; Bowerbank, Geol. Proc., 1840; and Micros. Journ., 1841.) Sponges are thus characterized, in accordance with the researches of Ellis and Grant, by Dr. Fleming (British Animals, p. 518): Sponges consist of an albuminous skeleton and gelatinous matter, forming a mass not irritable, with numerous holes, connected internally with anastamosing canals. The skeleton is either simple, consisting of horny fibres, as the species so commonly used for domestic purposes; or compound, being strengthened by calcareous or siliceous spicula.* The gelatinous matter, abounding in Some of the skeletons of sponges are (perhaps) entirely horny; others, as in a beautiful specimen from the West Indies which M. Stuchbury has shown us at Bristol, are entirely siliceous; possibly some are entirely calcareous; but the greater number are compound, and consist of horny matter with additions spicula in various proportions. is then cut into cylindrical or other forms. The pieces are introduced into sinuses and other narrow canals, with the intention of dilating them by the expansion of the sponge, when the wax melts by the heat of the part. Sponge tents are however little used by modern surgeons. According to the analysis of Hornemann, sponge consists of a substance similar to osmazome, animal mucus, fat oil, a substance soluble in water, a substance only soluble in potash, and traces of chloride of sodium, iodine, sulphur, phosphate of lime (?), silica, alumina, and magnesia. When sponge has been cut into pieces, beaten in order to free it from little stones and shells, and burnt in a closed iron vessel, till it is black and friable, it is then called burnt sponge (spongia usta), and has in 1000 parts the following composition, according to Preuss :-343 parts are destroyed by heat; the remaining parts are-carbon and siliceous insoluble matters, 327; chloride of sodium, 112; sulphate of lime, 16; iodide of sodium, 21; bromide of magnesium, 7; carbonate of lime, 103; magnesia, 4; protoxide of iron, 28, and phosphate of lime, 35. As the virtues of this greatly depend on the proportion of iodine, much of which is volatilized by the high temperature required to calcine the sponge, it has been proposed only to expose it to such a heat as will thoroughly dry, and colour it brown, and render it friable, when it may be powdered, and preserved in well-closed bottles. For use it is generally formed into an electuary or into lozenges. A test of its goodness consists in heating it in a glass flask with sulphuric acid, and if copious violet-coloured fumes be evolved, this proves that it contains much iodine. Burnt sponge has been almost completely superseded in the treatment of bronchocele and scrophula by iodine and its preparations; but as it obviously consists of a natural combination of many of the principles which have been deemed useful in scrophula, it ought not to be hastily discarded. It is with great propriety retained in the Dublin Pharmacopoeia. SPO'NGIADE. Regarding sponges as Apolypiferous Zoophyta, composed of flexible or rigid skeletons enveloped in a gelatinous mass, productive of inward currents through small surface pores, and outward currents through continuous canals, we may proceed to analyse the large group of organic forms possessing these characters, by the nature and arrangement of the skeleton, for the gelatinous part (though perhaps conservable, if due care be used) is not probably capable of being examined so as to furnish distinctive and recognisable characters. Dr. Grant pointed out the principles of this analysis, by his observations on the nature and arrangement of the horny fibres, the calcareous and silicious spicula, and the formation and distribution of the pores and orifices of sponges. Dr. Fleming (British Animals) gives the following genera, under the family of Spongiada:-Tethya, Halichondria (including Spongilla of Lamarck), Spongia, Grantia. (Siphonia, Choanites, and Ventriculites of Parkinson and Mantell are included in Halichondria.) Blainville (Actinologie) arranges under the head of Amorphozoa Alcyonellum, Spongia, Calcispongia (Grantia, Fleming), Halispongia, Spongilla (Ephidatia, Lamouroux), Geodia, Coeloptychium (fossil), Siphonia, Myrmecium (fossil), Scyphia, Eudea (fossil), Halirrhoa (fossil), Hippalimus (fossil), Cnemidium (fossil), Lymnorea (fossil), Chenendopora (fossil), Tragos (fossil), Manon (fossil), Ierea (fossil), Tethium. Very few of these genera, adopted from Schweigger, Goldfuss, and others, can be considered as at all sufficiently determined, because the constituent structures of the fossil masses, on which alone they can be justly founded, have, in most cases, been altogether left unexamined. When the modern achromatic microscope shall have been directed upon them, with such perseverance as Mr. Bowerbank (Proceedings of Geol. Soc., 1840) has employed on the spicular structures of the sponges imbedded in or constituting the nodules of flint in chalk, so that the forms of the anastomosing fibres or stiffening spicula, the sections and distribution of the canals, &c., can be certainly defined, a great benefit will arise to this branch of zoology, and an equal advantage for geology. Groups of which the Constituent Structure is known. SPONGIA.-Mass soft, elastic, more or less irregular in shape, very porous, traversed by many tortuous canals which terminate at the surface in distinct orifices. Substance of the skeleton, cartilaginous fibres anastomosed in all directions, without any earthy spicula. Example, Spongia communis. (Blainville's Actinologie, pl. 93, fig. 3.) Calcispongia, Blainville (Grantia, Fleming; Luchelia, Grant)-Mass rigid, or slightly elastic; of irregular form, porous, traversed by irregular canals, which terminate on the surface in distinct orifices. Substance of the skeleton cartilaginous fibres, strengthened by calcareous spicula. The spicula are seldom simple, often triradiate in figure. Example, Calispongia compressa. (Montague, in Wern. Trans., vol. ii., pl. 12.) Altogether Fleming and Blainville admit five species of this genus as determined.. They occur on the British and other northern shores. Examples, Spongilla fluviatilis, Linn.: Spongilla lacus. tris, Lin. For the animal nature of these fresh-water sponges the argument is less complete than for the marine tribes. By experiments as to the effect of light on them, Mr. John Hogg (Linn. Trans.) has endeavoured to show that they are influenced by this agent in the same manner as plants are, and that their green colour depends upon exposure to it. Groups depending on Characters of Surface or general Figure. Geodia, Lamarck.-Mass fleshy, tuberous, irregular, hollow within, externally incrusted by a porous envelope, which bears a series of orifices in a small tubercular space. Example, Geodia gibberosa, Schweigger. (Blainville, Actinologie, pl. 91, fig. 4.) Coeloptychium, Goldfuss.-Mass fixed, pedicled, the upper part expanded, agariciform, concave, and radiato-porose above, flat and radiato-sulcate below. Substance fibrous. Example, Coeloptychium agaricioideum, Goldfuss. (Petrefactenkunde, pl. 9. fig. 20, a—e.) From the chalk of Westphalia. Siphonia, Parkinson.-Mass polymorphous, free or fixed, ramose or simple, concave or fistulous above, porous at the surface, and penetrated by anastomosing canals, which terminate in subradiating orifices within the cup. Example, living, Siphonia typum. (Blainville, Actinologie, pl. 95, fig. 1.) Sicily. Example, fossil, S. pyriformis, Goldfuss. (Petrefactenk, tab. 6, fig. 7, a, b, c, d, e.) Siphonia abound in the green-sand formation. Myrmecium, Goldfuss.-Mass subglobular, sessile, of a close fibrous texture, forming ramified canals which radiate from the base to the circumference; summit with a central pit. Example, Myrmecium hemisphericum, Goldfuss. (Petref., tab. 6.) Scyphia, Oken.-Mass cylindrical, simple, or branched, fistulous, ending in a large rounded pit, and composed entirely of a reticulated (firm) tissue. Example, living, S. fistularis, Esper. (Tab. 20, fig. 2.) Example, fossil, S. mammillaris, Goldf. (Petref., tab. 2, fig. 1.) Eudea, Lamouroux.-Mass filiform, attenuated, subpedicellated at one end, the other enlarged, rounded, with a large terminal pit; surface reticulated by irregular lacunæ, minutely porous. Example, Eudea clavata, Lamouroux. (Gen. des Polup, tab. 74, fig. 1-4.) Halirrhoa, Lamouroux.-Mass turbinated, nearly regular, circular, or lobate; surface porous; a large central pit on the upper face. Example, Halirrhoa costata, Lamouroux. (Gen. des Polyp., pl. 78, fig. 1.) From the oolite of Caen. Halispongia, Blainville (Halichondria, Fleming).- Mass more or less rigid or friable, irregular, porous, traversed by tortuous irregular canals, which terminate at the surface in distinct orifices. Substance cartilaginous, fibres strengthened by silicious (generally fusiform or cylindrical) spicula.gins. Example, Halispongia papillaris, Grant. (New Edinb. Journal, vol. ii., tab. 11, f. 21.) Blainville admits fourteen species. Fleming, who includes in it the fresh-water spongilla (Ephydatia, Lamouroux), counts eighteen species. In what manner the immense number of species of sponges mentioned by Montague and Lamarck are to be distributed among these three groups, which ought to be considered families rather than genera, does not appear. The remarkable silicious sponge which has been before alluded to [SPONGIA] as under examination by Mr. Stutchbury of Bristol, would appear justly entitled to constitute a new genus, if, as we suppose, it is in no manner dependent for its figure on a cartilaginous skeleton, but is really and entirely a silicious mass, supporting a gelatinous envelope. Spongilla, Lamarck and Blainville (Ephydatia, Lamourouc).-Mass more or less rigid or friable, irregular, porous, but not furnished with regular orifices to internal canals. Cnemidium, Goldfuss. - Mass turbinated, sessile, composed of close fibres and horizontal canals, diverging from the centre to the circumference; a central pit on the upper surface, cariose in the exterior, and radiated at the mar Example, Cnemidium lamellosum, Goldf. (Petref., tab. 6, fig. 1.) Lymnorea, Lamouroux.-Masses mammellated, finely porous and reticulated, agglomerated within a common calyciform wrinkled adherent base. Example, Lymnorea mammillosa, Lamouroux. (Gen des Polyp., tab. 79, fig. 2.) From the oolite of Caen. Chenendopora, Larnouroux.-Mass conical, infundibuliform, external surface sulcated across, internal face porose. Example, Chenendopora fungiformis, Lamouroux. (Gen. des Polyp., pl. 75, fig. 10.) From the oolite of Caen. Tragos, Schweigger.-Mass composed of dense, close, coalescing fibres; surface covered by distinct scattered or fices. Example, Tragos difforme, Goldfuss. (Petref., tab. 5, fig. 3.) |