CiRRHOPODA.] 



MUSEUM OF ANIMATED NATURE. 



291 



nified : a, the tegumentary body of the trunk, which 

 is seen within; b, the pouch or tunic enclosing the 

 body of the young animal, which is surrounded by 

 a nutritive vitelline fluid; b", appendages termi- 

 nating in suckers and enabling the animal to fix 

 itself; a*, the tail, formed by a prolongation of the 

 tegumentary investment, and enclosing a tubular 

 appendage of the vitelline sac. This tail is cast off 

 when the animals quit the larva state and assume 

 their sessile and aggregated condition. 



It is to Milne Edwards that we owe our know- 

 ledge of the metamorphoses of these singular ani- 

 mals. See 'Ann. des Sci. Nat.' 1828, tom. xv., 

 p. 10, and also the paper by Milne Edwards enti- 

 tled ' Observations sur les Ascidies composees, des 

 Cotes de la Manche,' read before the French Aca- 

 demy of Sciences, November 11, 1839, in which the 

 physiology of these interesting animals is deeply 

 investigated. 



Fig. 3047 represents a fossil from- the lower 

 Ludlow rock, regarded as belonging to the Asci- 

 dian Tunicata. 



Mr. Murchison remarks that these curious fossils 

 are so grouped together, that he always compared 

 them with packed or baked figs, and he says that 

 Mr. Konig, to whom he referred them, thus speaks 

 of them :— " I am of opinion that they may be con- 

 sidered to belong to the family of the Ascidiae. . . . 

 They seem to form a group of globular cariceous, 

 and, if may be added, pedicled bodies, for in one of 

 them the cicatrix (or mark) for the insertion of the 

 pedicle distinctly appears. As, however, no traces 

 of branchial or other apertures are to be found on 

 the surface exposed to view, it would be rash to 

 constitute this fossil a genus, or assign it a place in 

 any of the known genera of naked mollusca." It is 

 the Ischadites Konigii of Mr. Murchison. 



CLASS BRACHIOPODA, Cuv. 



(Palliobranckiaia, De Blainville, Owen, &c.) The 

 class Brachiopoda, or Palliobranchiata, includes 

 three groups, Tcrebratula, Lingula, and Orbicula, 

 of which the species are all tenants of a bi-valve 

 shell ; but they difier so essentially from the ordi- 

 nary mollusca of bi-valve shells, that their separation 

 into a distinct class is abundantly justified. In 

 common with the Barnacles, or Bernicles, the spe- 

 cies of Lingula and Terebratula are affixed by means 

 of a fleshy tubular pedicle to submarine bodies. In 

 Orbicula, on the contrary, the pedicle is wanting, as 

 in the Balani, and the lower valve of the shell be- 

 comes itself the medium by which the attachment 

 of the animal to the rock is effected. In Lingula 

 and Terebratula, the larger of the two shells is 

 pierced at its summit or umbo for the passage of the 

 pedicle. 



The body of these moUusks within the shell is 

 covered with a delicate mantle, lining the inside of 

 the valves, and this mantle, which is traversed by 

 blood-vessels, and furnished, especially along its 

 edge, with vibratile cilia, constitutes the respiratory 

 apparatus, whence the term Palliobranchiata (Pal- 

 lium, a mantle), mantle-gilled. 



In addition to this singularity of structure, the 

 organs for procuring food offer many remarkable 

 structural peculiaritie*. 



They consist of two long spiral arms, one on each 

 side of the mouth, and in many species these are 

 capable not only of being unrolled, but extended 

 beyond the shell to a great distance in quest of 

 food. They are usually furnished with numerous 

 vibratory filaments for the more certain capture of 

 the prey. They also appear to act as oars, enabling 

 the animal slightly to alter its position. It is to 

 these arms that Cuvier's title Brachiopoda alludes. 



In Terebratula the two valves are unequal, one 

 being more convex than the other, and pierced at 

 its apex with an orifice for the transmission of the 

 peduncle, by which the animal is moored to stones, 

 corals, &c. The other valve is flatter and imper- 

 forate, and presents us on its inner surface with a 

 curious framework of shelly matter, consisting of a 

 slender calcareous loop, fixed at its extremities to 

 the lateral ridges of the hinge. This loop at first 

 advances, and is then suddenly bent back upon 

 itself, and at this point is attached to two processes, 

 branching off from a raised line or ridge, running 

 down the centre of the valve. This remarkable 

 framework serves as a defence to the viscera, and 

 as a support to the arms, which are fringed with long 

 cilia. In some species, as T. chilensis and T. trun- 

 cata, the arms are not extensile ; but in T. Psittacea, 

 of which Professor Owen, in the 'Trans. Zool. Soc.,' 

 vol. i., gives an admirable account, the arms are 

 enormously developed, fringed along their outer 

 margins, and quite free except at their origin. In 

 their retracted state they are disposed in six or 

 seven spiral folds, but when stretched forth extend 

 beyond the shell to twice its length. 



fhe mechanism by which these arms are unfolded 

 is simple, yet curious. The stem of each arm is 

 Vot II. 



tubular, and contains a fluid, which, acted upon by a 

 multitude of muscles, forming the walls of the canal, 

 and arranged spirally, is forced onwards up the tube, 

 and thus the arm is expanded and protruded through 

 the gaping valves. 



The arms of these animals are essentially service- 

 able in procuring food, and having nothing to do, 

 gill-like as they appear, with respiration or the re- 

 novation of the circulating fluids, for their cilia have 

 horny texture, and do not exhibit any high degree 

 of vascularity. Their object is by their movements 

 to produce a current of water to the mouth, which 

 hurries with it the nutritive particles with which the 

 fluid is charged. We may here notice some re- 

 markable muscular peculiarities in Terebratula. 

 Two pairs of muscles arise from each valve, those 

 of the imperforate valve at a distance from each 

 other; one pair arise near the centre of the valve, 

 and these converging unite below the stomach ; 

 these then divide and pass through the foramen of 

 the perforate valve, to be inserted into the pedicle. 

 The other pair are short and fleshy, and arise from 

 depressions near the centre of the hinge ; they are 

 also inserted into the pedicle. 



Of the perforate valve the muscles arise close 

 together, so as to leave impressions on each side of 

 a supposed median line ; one pair is inserted into 

 the pedicle, the others are adductors of the valves, 

 and merely pass from the one to the other. 



Fossil Terebratulse are extremely numerous, and 

 occur in abundance in some of the older strata to 

 the supracretaceous group. The recent species are 

 numerous, and widely dift'used from the equinoctial 

 to the polar seas. The depth at v^hich they are 

 found varies from ten to ninety fathoms. 



Of the different variations of form presented by 

 Terebratula and its subgenera our pictorial speci- 

 mens will give a good idea. 



Fig. 3043 represents the shell of Terebratula di- 

 gona ; the border is straight, as if cut oft". It is only 

 found in a fossil state. 



Fig. 3049 is the shell of Terebratula globosa : a 

 living species. 



Fig. 3050 shows the valves of Terebratula dorsata ; 

 on the inner surface of one of which is seen the 

 loop. It is one of the recent species. 



Fig. 3051 is a fossil species, Terebratula deformis. 



Fig. 3052 is another fossil species, Terebratula 

 alata. 



Fig. 3053 is Terebratula rubra, a recent species. 



Fig. 3054 is the Terebratula Caput Serpentis, a 

 recent species. 



Fig. 3055 is the Terebratula Lyra, known as fos- 

 sil only. 



Fig. 3056, Terebratula canalifera, fossil. 



Fig. 3057 is the Strigocephalus Burtini, fossil. 



Fig. 3058 is the Spirifer trigonalis, fossil. 



Fig. 3059 is the Magas pumilus, fossil. 



Fig. 3060 is the Producta Martini, fossil. 



In the genus Magas the system of support is be- 

 ginning to disappear, and in Producta the lower 

 valve is not perforated at its summit, but is divided 

 into two equal parts by a distinct transverse suture. 

 (See Martin's Petrificata Derbiensia, t. 22, fig. 1,2, 3.) 

 It is here, perhaps, as a link between Terebratula and 

 Orbicula, that the genera Thecideum and Stropho- 

 mena will range. 



The genus Thecideum is characterized by the 

 shell being equilateral, but very inequivalve : one 

 valve is hollowed, the heel or hook recurved and 

 entire, without fissure ; the other fiat, and without 

 trace of internal support. The animal is unknown, 

 but probably resembles that of Orbicula. One living 

 species (Th. mediterraneum) is found in the Mediter- 

 ranean. Fig. 3061 represents Thecideum radiatum ; 

 a, the natural size. 



In the genus Strophomena.the shell is subequi- 

 valve ; one valve is flat, the other somewhat exca- 

 vated. There is no trace of an internal support. 

 No living species. Fig. 3062 represents the Stro- 

 phomena rugosa. 



We now turn to the genus Lingula. 



In this genus the pedicle is very long, cartilagi- 

 nous, and nearly cylindrical. The testaceous valves 

 are somevfhat elongated, compressed, truncated an- 

 teriorly, and acted upon by adductor muscles ob- 

 liquely placed. On opening the valves the animal 

 appears enclosed between two delicate membranes, 

 forming the mantle. The margins of this mantle 

 are thickened and fringed with delicate vibratile 

 cilia. The mouth opens at the summit of a promi- 

 nence, and on each side spread out the arms, which 

 are fleshy, flat, and fringed ; when contracted they 

 roll up in a spiral manner, and can be uncoiled and 

 protruded to a considerable extent from the shell. 



The Lingula is generally supposed to be moored 

 or attached by its peduncle, but in the specimen of 

 L. Audebardii, examined by Professor Owen, there 

 was no trace of the adhesion of any foreign body to 

 the extremity of the peduncle. 



Fig. 3063 represents the Lingula anatina, a native 

 of the Indian seas. The valves are thin, horny, and 

 greenish. 



We now turn to the genus Orbicula. 



In Orbicula there is no peduncle ; and the two 

 valves differ in form and size. One is conical and 

 rounded, somewhat resembling the shell of a limpet, 

 and has been regarded as a Patella by the oWer 

 writers. The other valve is flat, with a fissure in 

 the centre, for the passage of a ligament by means 

 of which it is fixed to the rocks. As in Lingula, 

 the mollusk has ciliated arms, rolled up spirally 

 when withdrawn. 



Fig. 3064 represents the Orbicula lamellosa. The 

 cilia of the mantle appear protruded through the 

 valves. The recent species of this genus are found 

 attached to stones, shells, and sunken wrecks, at va. 

 rious depths to seventeen fathoms. The Orbicula 

 lamellosa is a native of the coasts of Peru ; it was 

 found by Mr. Cuming in groups, the individuals 

 being in many instances piled in layers one over the 

 other, on a sandy bottom at a depth ranging from 

 five to nine fathoms. At Ancon they were found 

 attached to dead shells, and also clinging to the 

 wreck of a Spanish vessel, of about three hundred 

 tons, which went down in the bay about twelve 

 years ago. The sunken timbers (for the sheathing 

 was gone to decay) were covered with these shells 

 much in the same way that beams on land are some- 

 times invested with flat parasitic fungi. At Inqui- 

 qui they were taken adhering to a living Mytilus. 

 See ' Proceeds. Zool. Soc' 1833, p. 124, and also 

 'Trans. Zool. Soc' i., for descriptions by Mr. Bro- 

 derip of several new species of Terebratula, Orbi- 

 cula, and Lingula. Fossil species occur in the 

 green-sand, oolite, and carboniferous limestone. 



The genus Crania is placed here by most zoolo- 

 gists. The upper valve is patelliform, the lower 

 valve is attached by its outside, the greater part of 

 it being generally extended over the substance to 

 which it adheres. There are four muscular impres- 

 sions on each valve. 



Fig. 3065 represents the Crania personata, the 

 only living species known. It dwells at great depths, 

 adhering to stones and shells ; and has been dredged 

 up in two hundred and fifty-five fathoms of water. 



Fossil species of this genus are found in the chalk. 

 Referring to Fig. 3065, a shows the shell viewed ex- 

 ternally ; b and c, inside views of the flat and con- 

 cave valves. In the 'Trans. Zool. Soc.,' vol. i., is an 

 admirable paper on the Brachiopoda, by Professor 

 Owen, to which we have already alluded ; and to 

 which we refer our readers for more full and minute 

 details. 



Here perhaps we ought to close the subkingdom 

 Mollusca, or Heterogangliata, Owen ; for the singu- 

 lar group of animals upon the general history of 

 which we are about to enter, though referred to the 

 Mollusca by Cuvier and preceding zoologists, cannot 

 but be regarded as coming within the pale of the 

 Crustacea, between which and the Annelids it ap- 

 pears to form a link of union. Cuvier, who was well 

 acquainted with the nervous system of the animals 

 of the group in question, namely, the Cirrhopods or 

 Cirripeds (bernicles, acorn-shells, Sec), observes 

 that they constitute in many respects an interme- 

 diate link between the Mollusca and the Articulata 

 (crabs and other Crustacea) ; yet we incline to the 

 views of Martin-Saint-Ange, who considers their 

 situation to be between the Crustacea and Annelids 

 — and were we devoting this work to an exposition 

 of the scientific arrangement of the animal kingdom, 

 such would be the station in which we would place 

 them. As this, however, is not our object, and as 

 zoologists are divided in their views on the subject, 

 we shall treat of them as a class per se, and leave 

 their situation open, only observing that while Mar- 

 tin-Saint-Ange considers them as Annelidian Crus- 

 tacea, M. de Blainville regards them as Crustaceous 

 Mollusks. 



CLASS CIRRHOPODA. 



The Cirrhopoda (Cirrhipeda, Cirripeda, or Cirri- 

 pedia) were all included by Linnaeus in the genus 

 I.epas, and placed among the Multivalves of his 

 Vermes, between Chiton and Pholas; and when we 

 reflect that their anatomy was not understood, we 

 shall not be surprised at his arrangement. This class 

 may be divided into two great sections, viz. the Pe- 

 dunculated Cirrhopods (Campylosomata, Leach,) 

 and the Sessile Cirrhopods (Acamptosomata, Leach). 

 All are marine ; in figure more or less conical ; 

 often compressed, and enclosed in a shell, of variable 

 form, and composed of many pieces, either soldered 

 or not soldered together. In one case only there is 

 no true shell, but a soft envelope in lieu of it. The 

 shell, or its representative, is either adherent to fo- 

 reign bodies by the intervention of a fleshy peduncle 

 issuing from the mantle, or is sessile and without a 

 peduncle. Within the shell the body is invested 

 with a sort of mantle, open on one side. There is 

 no distinct head ; no eyes, and no true tentacula ; 

 but from the apical portion of the body emerge a 

 certain number of jointed and ciliated cirrhi. The 



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