Gastrocii.t.na.] 



MUSEUM OF ANIMATED NATURE. 



287 



in those instances in wliicli it lias not perforated at 

 all, but in which it has taken up its abode in the 

 recesses of some empty shell. This will be best 

 understood by the reference to our pictorial spe- 

 cimens. 



At t'lg. 3020, A shows a group of the tubes of the 

 Gastrocha;na modiolina, Lam., from the Mediterra- 

 nean. A has the tube broken, displaying the en- 

 shrouded shell in situ. B is a specimen of the 

 anterior portion of a fossil spindle (Fusus Noae), 

 from Grii^non, cut open and displaying the small 

 clavate tube of a fossil Gastrochaena which had 

 taken its lodirment there. C, a worn fragment of 

 madrepore, broken open to show the tube formed 

 by a specimen of Gastrochaena cuneiformis. D and 

 'E, the shell of Gastrochsena cuneiformis, in two 

 views. 



Fossil Gastrochaenae are not numerous ; one species 

 occurs in the inferior oolite. 



We may here advert to the genus Fistulana, 

 between which and the preceding the grounds of 

 distinction appear to be somewhat doubtful. M. 

 Deshayes, indeed, has proposed to sink the genus 

 Gastrochaena, but, with the same view, M. de 

 Blainville would, if both eenera be inadmissible, 

 rather suppress the genus Fistulana, because it was 

 established subsequently to Gastrochoena ; on the 

 whole, however, he prefers its restriction, as in his 

 ' Malacologie,' to its entire suppression. M. Rang 

 observes that two of the species of Fistulana of 

 Lamarck belong, as M. de Blainville correctly 

 deems, to Ga-strochaena, viz., Fistulana clava and 

 Fistulana ampullaria. With regard to the latter, 

 M. Deshayes, who retains it in the genus Fistularia, 

 says, that according to circumstances it forms a free 

 tube sunk in the sand, or, on the contrary, perforates 

 calcareous bodies, its tube then serving as a lining 

 to the cavity it inhabits. In the (irst case, there- 

 fore, this species would belong to Fistulana — in the 

 second case to the genus Gastrochaena, if indeed 

 that genus must be preserved. 



From all this, it appears that the two genera in 

 question are mere sections of one generic group, 

 by whatever title it may be considered most con- 

 venient to designate that genus. 



Fig. 3021 represents the Fistulana clava, Sowerby ; 

 Gastrochaena clava, llang and De Blainville. 



This species is a native of the Indian Seas ; it 

 shrouds itself within a tube, always complete and 

 free, and is found imbedded in sand or hard mud, 

 with the small end of the tube uppermost. 



Referring to the figures, A represents the tube 

 of this species, which often presents a septum, seen 

 at a; B, the valves of the shell, outside view; C, 

 an internal view of the valves of the shell ; D, apex 

 of tube. 



We may now turn to that interesting genus 

 Clavagella, which has recently engaged the atten- 

 tion of some of the most scientific zoologists of 

 Europe. 



This genus was founded by Lamarck on certain 

 fossil species ; and these only for many years were 

 known as the only representative of the form in 

 question. 



The first discovery of a recent species of Clava- 

 gella is due to Mr. George Sowerby, who detected 

 a specimen enclosed in a mass of stone in the 

 British .Museum. Having obtained permission, he 

 scraped away the stone, and thereby brought into 

 view the shell, which, under the name of Clavagella 

 aperta, the first recorded recent species, he described 

 and figured in his ' Genera of Recent and Fossil 

 Shells.' 



Soon afterwards, 1827, the same zealous naturalist 

 was enabled to add another recent species to the 

 genus. This was brought home by Mr. Stutchbury, 

 who with some difficulty obtained three specimens 

 at North Harbour, Port Jackson, during his voyage 

 to Australia ; they were imbedded in a siliceous 

 grit, and their presence was betrayed just beneath 

 low-water mark by the jets of water which they 

 forcibly ejected from their tubes. To this species 

 Mr. G. Sowerby gave the name of Clavagella 

 Austral is. 



In 1829 Mr. Stutchbury detected a Clavagella 

 embedded in a mass of coraline, in the collection 

 of Mr. J. L. Goldsmid, and to this Mr. Broderip 

 gave the name of Clavagella elongata. (See ' Pro- 

 ceeds. Zool. Soc' 1831, p. UG.) 



Besides these, M. Audouin described a recent 

 species, and M. Rang another, under the title of 

 Clavagella Rapa. (See 'Ann. des So. Nat.' tome 

 xvii. p. 78 ; and Rang'* ' Manuel des MoUusques,' 

 1829.) 



On the return of Mr. Cuming from his first 

 voyage, among the valuable collection of that enter- 

 prising conchologist were specimens of Clavagellae 

 submitted to the inspection of Mr. Broderip. Of 

 these one was embedcfed in a fragment of calcareous 

 grit dredged up from a depth ol eleven fathoms, at 

 the island of Mu'Tte, in the Bay of Guayaquil. This 

 is described by Mr, Broderip as the Clavagella lata. 

 (.' Proceeds. Zool. Soc' 1831.) The other species 



was from Malta, and is termed Clavagella Melitensis. 

 (' Proceeds. Zool. Soc.') Mr. Broderip observes that 

 " it is not impossible, from its locality, that this may 

 turn out to be M. Audouin's species, if it should 

 prove to be a true Clavagella." (See also ' Trans. 

 Zool. Soc' vol. i.) 



To these must be added two species from the 

 Mediterranean, described, one, by Delle Chiaje, as 

 Clavagella Sicula ; the other, by Scacchi, as Clava- 

 gella Balanorum. 



M. Cailliaud, in an admirable paper published in 

 the ' Magasin de Zoologie,' 1842, in which he gives 

 the results of his own personal observations on the 

 species collected in the Mediterranean and Adriatic 

 seas, refers the Clavagella lata, Brod., and the 

 Clavagella Sicula, to the Clavagella aperta of 

 Sowerby ; the differences being the result of age, 

 &c. If so, the distribution of the same species 

 must be extremely wide. In the ' Trans. Zool. Soc' 

 vol. i. will be found an elaborate paper, by Pro- 

 fessor Owen, on the anatomy of the Clavagella lata, 

 Brod., from the specimen brought home by Mr. 

 Cuming, who carefully placed the animal in spirits 

 soon after its capture. 



We shall not attempt to follow the Professor 

 through his details, but content ourselves by refer- 

 ring to the specimens at Fig. 3022 : — A, a 

 part of the calcareous grit rock containing the 

 fixed valve and part of the tube of Clavagella 

 lata ; C, an external view of the right or free 

 valve ; D, internal view of the same ; B, the soft 

 parts of the mollusk seen from the right side ; 

 the dermal layer of the mantle, e, being removed ; 

 E, the same seen from the left side, or that which 

 is in contact with the fixed valve. The extremities 

 of the left labial appendage are exposed, no part 

 of the gill being protruded ; a bristle (*) is placed at 

 the opening of the mantle ; a, the anterior wall of 

 the chamber ; b, dorsal wall, the latter placed on 

 the hinge of the fixed valve ; c, the ventral wall ; 

 rf, the posterior or siphonic outlet; e, tubular com- 

 munications with a neighbouring cavity, here set 

 off from the posterior part of the mantle ; e' e' , cal- 

 careous tubes secreted by the above processes and 

 extending into the cavities contiguous to the throat 

 of the tube; c", a cavity communicating with the 

 anterior part of the chamber; f, impression of 

 posterior adductor muscle ; g' , impression of an- 

 terior adductor muscle ; h' , impression of pallial 

 muscle, or third adductor; /, posterior adductor; 

 <7, anterior or smaller adductor ; li, pallial adductor ; 

 i, convex muscular mass, analogous to the muscular 

 margin of the mantle lobes in other mollusks ; k, 

 muscular fibres of siphon; F, I, respiratory or inges- 

 tive siphonic canal ; m, egestive siphonic canal ; 

 n (E), labial appendage; t (B), the gills; x, part 

 of egg-sac ; G, anterior termination of shelly 

 tube. 



M. Cailliaud gives the following characters of 

 Clavagella : — Shell bivalve, attached to a free tube 

 in the fossil species, but in the living state in- 

 cluded in calcaieous masses or some marine pro- 

 duction ; the anterior part of the tube open, in the 

 form of a ruffled chalice ; the posterior part, exca- 

 vated, oval, containing one valve free and another 

 fixed to its wall ; ligament external. 



Mr. Broderip observes that we are left to con- 

 jecture the causes which operate to determine the 

 animal in the choice of its abode, if indeed it can 

 be called choice, for most probably Clavagella is 

 the creature of circumstances, and if, soon after ils 

 exclusion from the parent (when Mr. Broderip sup- 

 poses it to be furnished with its two valves only, 

 and to float free with perhaps some voluntary im- 

 pulse), it arrives at the vacant hole of some small 

 Petricola, Lithodomus, or other perforating testa- 

 cean which suits it, one valve soon becomes at- 

 tached to the wall of the hole, and the animal pro- 

 ceeds to secrete the siphonic sheath or tube, to 

 enlarge the chamber according to its necessities, and 

 to form the shelly perforated tubular plate, which is 

 to give admission tothe water at the practicable part 

 of the chamber. Though Mr. Broderip observes that 

 the means by which the excavation i-t carried on are 

 doubtful, he is inclined to attribute it to some solvent 

 secretion of extensive power, the true nature of 

 which is not known. In this opinion Mr. Broderip 

 is followed by M. Cailliaud, who adduces many 

 ingenious and forcible arguments in favour of these 

 views, from facts which have come under his own 

 observation. 



At Fig 3023 is represented a series of specimens 

 of Clavagella aperta illustrating its growth : a is 

 the right valve of a very young individual; b, the 

 same more advanced, seen in the stone, which has 

 been cut to show the excavated part, and the right 

 valve in situ ; its young tube has six facets and 

 developes its first firnbriation or niffle ; c, the 

 same still further advanced, also in the stone : its 

 young tube has two ruffles ; d, the same greatly 

 increased and seen in the stone : a part of the mollusk 

 is seen under the right valve, and in its excavation ; 

 also the great muscle of the mantle, and the aper- 



ture whence its small rudimentary foot comes forth. 

 The lower extremity of the tube is laid open, 

 to show the siphons terminating in papillae. The 

 tubes present five ruffles, and the commencement 

 of two others, which the mollusk had not finished. 

 Fig. 3024 is another specimen, which had entered 

 the stone horizontally, and afterwards had prolonged 

 its tube in a perpendicular direction ; Fig. 3025, 

 another specimen. 



Figs. 3026 and 3027 are two specimens of tne 

 Clavagella Balanorum, imbedded in an aaglomera- 

 tion of Balini (sessile barnacles). A series of little 

 tubes like fibres may be seen binding the animal in 

 the upper figure to the base of stone. 



M. Cailliaud observes that, both in the living 

 Clavagellac and also in the fossil species, small 

 tubes often co-adapted (accol6s) to each other, are 

 placed in various parts of the cell. M. Rang be- 

 lieved that these served to give passage to so many 

 fasciculi of byssus with which the animal is attached 

 to the bottom of its dwelling. But M. Cailliaud 

 remarks that this supposition cannot be allowed ; 

 for they would be entirely useless to the mollusk, 

 which IS sufficiently attached by its fixed valve. 

 An attentive examination of these little tubes in 

 living Clavagellse has proved to M. Cailliaud that 

 their use was not to afford a passage to the water, 

 as has also been supposed, because in many of the 

 excavations there are neither tubes nor any other 

 communications ; that the animal had no l)yssus ; 

 but that their utility was to fill the vacant spaces 

 which the mollusk meets with in the stone, and which 

 have sometimes been made by other perforating 

 animals. Accordingly we perceive that these 

 tubular reunions are always due to chance : one 

 sometimes sees them at the bottom of the dwelling 

 of the mollusk, sometimes in the walls; wherever 

 in fact there is a necessity for closing up, but never 

 with any fixed character. 



'M. Cailliaud goes on to state that one of the most 

 curious facts is the manner in which these small 

 pipes are formed. The epidermis of the great 

 muscle of the mantle is rough, covered with 

 small pustules, wh'nce fleshy filaments, like 

 tentacles, occasionally come forth : these are so 

 many instruments whence the secreting matter is 

 poured out, and with which the mollusk forms 

 those little tubes which are shown in the figure of 

 Clavagella Balanorum. M. Cailliaud had not been 

 able to see them positively in action, when M. 

 Scacchi of Naples twice surprised these animals in 

 the act of introducing these fleshy filaments into 

 the commenced tubes, which they secreted in a 

 short time ; many finished ones were already closed, 

 and when the work was completed these filaments 

 retired into the epidermis of the great muscle, tore- 

 appear again when necessity required their aid. 



We now pass to the genus Aspergillum (Les 

 Arrosoirs of the French). 



In this singular genus, the affinities of which 

 were correctly appreciated by Lamarck, we find 

 a mollusk sheathed in an elongated cone, closed 

 at the large end by a disc, pierced with a 

 great number of tubular orifices; the little tubes 

 forming the outer row are the longest, forming a 

 sort of corolla round the disc. At a little dis- 

 tance above this base two small valves incrusted 

 in the substance of the tube are easily distin- 

 guishable. Besides the little tubular processes of 

 the disc, which, it would seem, contribute to sub- 

 port the Aspergillum upright in the sand, into 

 which it is perpendicularly plunged, there is a small 

 open fissure, admitting water into the dwelling, 

 necessary perhaps, in low tides, when the upper 

 extremity of the tube is above the level of the sur- 

 face of the sea. 



The animals of this genus are borers: some live 

 in the sand, plunged down perpendicularly for 

 about three-fourths of their length ; some burrow 

 in stone, others in wood, and others again in thick 

 shells. 



Fig. 3028 represents the Javanese Aspergillum, 

 Aspergillum Javanum: a indicates the valves in- 

 crusted in the tube ; b exhibits a front view of the 

 disc. 



This species is a native of the Indian Ocean. It 

 attains to seven or eight inches in length. 



Fig. 30J9 represents the Aspergillum vaginife- 

 rum : a, the two valves incrusted in the tube. 

 This species inhabits the Red Sea, and has been 

 found there by M. Riippel. 



Fig. 3030 represents the Aspergillum Novae Zea- 

 landiae : a, the valves incrusted in the tube ; b, a 

 front view of the disc. 



This species of Aspergillum occurs on the coast 

 of New Zealand. 



Here, tlien, we close our sketch of the Conchifera, 

 the Acephalous Bivalve Mollusca ; the leading struc- 

 tural points of which we trust we have not alto- 

 gether failed in explaining. Let it be remembered 

 that we write not for the scientitic zoologist, but for 

 those who desire a general acquaintance with the 

 great groups of the animal creation. 



