CLADYODON. 



CLAVAGELLA. 



(Lindley, Flora Mcdica ; Burnett, Ou'lincs of Botany; Hooker, 

 Iftitish Flora, vol. ii.) 



CLADYODOX, a generic title for some Fossil Tleptiles found in the 

 New Red-Sandstone System. [THECODOSTS.] 

 CLARIS. [BERNICLE GOOSE.] 



CLAXGULA, a genus of Birds belonging to the family Anatldce. 

 CLARY. [SALVIA.] 



CLATHRA'RIA, a genus of Fossil Plants found in the Wealden 

 strata of Sussex by Dr. Mantell. The stem is reticulated on the 

 surface, and has analogies to Xantfiorrhcea and the Cycadew. Clatk- 

 rariaLyellii and C'l. Mantelli (t'lis latter the fruit) are described by 

 Brongniart (' Hist, des Veg^t. Foss.'). 



CLATHRO'PTERIS, a remarkable genus of Fossil Ferns, the 

 foliation of which is marked with quadrangular network of vessels 

 a rare circumstance in living ferns such as Mmiacium. Clnthropteru 

 mtniscioides occurs in the Mesozoic Sandstone of Hor in Scania. 

 CLAUSILIA, a genus of Palmoniferous MoUusca. [HELICID.E.] 

 CLAVAGELLA, a genus of Testaceous Acephalous Animals, 

 established by Lamarck in the fifth volume of the ' Histoire 

 Naturelle des Animaux sans Vertebres,' published in 1818, and 

 arranged by him under his TubicoliSes, between Aspergillum and 

 Fittulana. He described four species, all fossil, referring at the same 

 time to the ' Annales du Museum," where he had figured the first of 

 them under the name of Fistulana echinata. Lamarck thus defines 

 the genus : '.' A tubular shelly sheath, attenuated and open ante- 

 riorly, terminated posteriorly in an ovate subcompressed club beset 

 with tubular spines ; the club presenting on one side the one valve 

 fired in its wall or substance, while the other valve remains free in 

 the tube." 



The genus was only known in a fossil state to conchologists, when 

 Mr. George Sowerby observed in the British Museum a recent speci- 

 men, which he at first thought might be an AipergiUum, inclosed in a 

 mass of stone. On application to Mr. Children, that gentleman 

 allowed Mr. Sowerby to examine it more closely, and on scraping 

 away some of the investing stone the latter found Clavagetta aperta, 

 the first recorded recent species, and figured and described it in his 

 ' Genera of Recent and Fossil Shells.' The same naturalist, on the 

 return of Mr. Samuel Stutchbury from his voyage to some of the 

 Australian and Polynesian Islands, described and figured (1827) a 

 second species, Ctrtragella australix, three specimens of which were 

 with difficulty obtained by Mr. Stutchbury at North Harbour, Port 

 Jackson, in a siliceous grit like that of the coal-measures, where their 

 presence was betrayed just beneath low-water mark, by their forcible 

 ejection of the water from the aperture of their tubes : the specimen 

 of Clavagella auttralii figured by Mr. Sowerby is also in the British 

 Museum. In 1829 Mr. Henry Stutchbury, in arranging the collection 

 of Mr. Isaac Lyon Goldsmid, suspected the presence of a Clavayella 

 in a mass of Astr&opora, and, on fracturing the specimen, laid open 

 two individuals of another species, Clnragella elongata, Broderip. 

 According to Cuvier, and a notice in the ' Annales des Sciences 

 Naturelles' (tome xvii., p. 78), M. Audouin (1829) described a recent 

 species, and M. Rang, in his ' Manuel des Mollusques' (1829), mentions 

 another, apparently Clavagella rapa. 



Still the animal remained unknown ; when, on the return of Mr. 

 Cuming from his first voyage, that zealous collector produced another 

 specimen which fortunately included the soft parts. A fragment of 

 calcareous grit was dredged up by Mr. Cuming from a depth of eleven 

 fathoms, at the island of Muerte, in the Bay of Guayaquil, and in this was 

 th<e greater portion of the chamber and tube, both valves, and the animal 

 of Clavagetla lata of Broderip. Mr. Broderip, who has described this 

 and two other recent species in the first volume of the * Transactions 

 of the Zoological Society ' (p. 261 ), says, that a close examination of 

 the recent species has convinced him that though one valve is always 

 fixed or imbedded in the chamber, and soldered, as it were, to the 

 tube, so as to make one surface with it, the tu-be is not necessarily 

 continued into a complete testaceous clavate shape. In Mr. Goldsmid's 

 best and largest specimen, the fixed valve was imbedded in the coral, 

 and though continued on to the tube or siphonic sheath, was sur- 

 rounded by the wall of the coral chamber at its anterior extremity. 

 In the other specimen the fixed valve was also continued on to the 

 tube. In the first-mentioned specimen of Clavagdla elongata, at the 

 anterior or greater end of the ovate chamber, an insulated or shelly 

 plate had been secreted with tubular perforations ; that part of the 

 chamber having afforded (apparently at a former period) the best 

 communication with the ambient fluid : but a calcareous deposit 

 having almost entirely cut off that communication, the animal seemed 

 to have been compelled to secrete a second shelly plate towards the 

 anterior ventral edge of the fixed valve, where the perforation of some 

 other shell (a Lithodomus probably) secured the necessary influx of 

 water. Nor is this the only instance of the secretion of a second 

 tubular plate which has fallen under Mr. Broderip's notice. In the 

 last-mentioned or smaller specimen, the perforated shelly plate joins 

 the anterior ventral edge of the fixed valve laterally, that point of the 

 chamber being evidently the most practicable for communicating with 

 the water by means of the tubule* : the rust (if the anterior edge of 

 the fixed valve is surrounded l>y tlie coral wall. In Mr. Cuming's 

 pecimen the fixed valve is continued on to the tube. The anterior 

 edge of this valve is surrounded by the naked wall of the chamber, 



and the greater end of the chamber, or that part of it which is oppo- 

 site to this anterior edge, being impracticable, from its thickness, as a 

 water communication (with a small exception, which, not improbably, 

 had ceased to be available), the animal had been driven to secrete the 

 perforated shelly plates not far from the throat of the tube on either 

 side, where the chambers of Pelricolce or Lithodomi opened a passage 

 to the surrounding water. 



Professor Owen, from an examination of Mr. Cuming's specimen, 

 has given an account of the anatomy of this mollusk. (' Zool. Trans.,' 

 vol. i.) He found the following to be the relative position of the 

 animal : The mouth turned towards the closed end of the chamber, 

 which is consequently the anterior part. The heart and rectum near 

 the side where the valves are connected by the ligament, or the dorsal 

 part. The visceral mass projecting towards the opposite or neutral 

 side. The siphon extending into the commencement of the calcare- 

 ous tube, which leads out of the anal or posterior part of the chamber. 

 The fixed valve, which covers the rough surface of the porous rock or 

 coral, like the tiling of a chamber-floor, and affords a smooth polished 

 surface for the support and attachment of the animal, is the left 

 valve: the right valve remains free, or is connected only to the soft 

 parts and cardinal ligament, in order to assist in the excavating and 

 respiratory actions. 



The shelly substance of the fixed valve passes without interruption 

 into that of the tube ; a slight ridge circumscribing the entry of the 

 tube into the chamber indicating the line of separation, unless the 

 extent of the valve be limited to that of the internal nacreous deposi- 

 tion. The tube of an oval form, 7 lines by 5 in diameter. The cal- 

 careous walls J,th of an inch in thickness at the outlet, and about ,th 

 at the opposite extremity. The free valve unequally triangular, with 

 the angles rounded off, about the thickness of a sixpence, moderately 

 concave towards the soft pai"ts, and striated only in the direction of 

 the layers of increment on the outer surface, as in most of the Pylori- 

 dean Bivalves of M. de Blaiuville. The layers gradually increase 

 towards the dorsal edge for a little more than one half of the valve, 

 beyond which the layers continue of almost equal breadth. " This 

 growth of the valve," adds Mr. Owen, " corresponds to the direction 

 in which the chamber is enlarged, which is principally on the dorsal, 

 dextral. and anterior sides : now this is the mode of enlargement best 

 adapted for the full development of the ovary ; so that it would seem 

 that the Clavagclla continues for a time to work its way into the rock 

 without material increase of size, leaving behind it a calcareous tube, 

 which marks its track ; after which it becomes stationary, and limits 

 its u|>i<rations to enlarging its chamber to the extent necessary for the 

 accomplishment of the great object of its existence." 



The mantle enveloping the body is like a shut sac, but perforated 

 for the siphon and foot, the opening for the latter being reduced to 

 a small slit. M. Riippell observed an analogous orifice in the corre- 

 sponding part in Aspergillum, namely, that which is next the sunken 

 sieve-like extremity of the tube, and by which he supposes the water 

 necessary for respiration to be received when the retreating tide 

 leaves exposed the expanded siphonic extremity. Professor Owen is 

 of opinion that this cannot be its use in those species of C'lavagclla 

 which exist at depths too great to allow of their being ever left 

 with the siphonic aperture out of water ; but that it must serve to 

 keep up a communication with the neighbouring cavities of the rock, 

 by means of the calcareous tubules, the formation of which is deter- 

 mined by the proximity of these cavities. When therefore the 

 Clavagella, by a sudden contraction of the adductor muscles, has 

 forcibly expelled the branchial currents from the siphon, as was 

 observed by Mr. Stutchbury, the space between the free valve and 

 the walls of the chamber would be simultaneously filled, either by 

 water rushing in through the tubules, or forced out from the branchial 

 cavity through the small anterior orifice of the mantle. To assist 

 this operation there is a proportional development of the muscular 

 system, which is remarkably powerful. The impression of the great 

 or posterior adductor is carried two lines beneath the surface of the 

 chamber posteriorly, but gradually rises to the level of the valve. 

 The impression of the smaller anterior adductor is more faint, and is 

 continued into the sinuous pallial impression, which follows the 

 contour of the anterior margin of the valve at about two lines' distance 

 from it. In the free valve the last two muscular impressions are 

 separate. The outer dermoid layer of the mantle is extremely thin, 

 and, where it does not line the valves, is mottled with minute dark 

 spots, less numerous than those on the skin of Cephalopods, and 

 presenting, uuder the microscope, a glandular appearance. Tho 

 muscular layer, after forming the siphon and its retractors, is confined 

 to the anterior part of the mantle, where it swells into a thick convex' 

 mass of interlaced and chiefly transverse fibres, and forming. 

 Professor Owen supposes, one of the principal instruments in the 

 work of excavation. No fibres could be detected in other parts of 

 the mantle ; nor could any be expected in a mantle which had no 

 lobes to be retracted. The siphon, in the contracted state, formed a 

 slightly-compressed cylindrical tube, half an inch in length, and the 

 sanu in the long diameter, traversed longitudinally by the branchial 

 ami anal canals, separated from each other by a muscular septum, 

 extending to the end of the siphon, beyond which the two tubes do 

 not separately extend outwards, agreeing in this respect with 

 Gaatrochama and Aspergillum. Muscular walls of the siphon two 



