HIT 



CLAVAcr.i.i.A, 



CLAVAOKLI-A. 



lisa 



line* in thickness; the aeptum separating the branchial and anal 

 canals one line ; diameter of each canal about one line ; inner 

 extremity both of the anal and respiratory tube provided with a 

 valvular fold : termination* beset with abort papilla;. The retractor 

 muscles attach the siphon to the posterior adductor on one side, and 

 to the anterior extremity of the oval max of muncular fibres above 

 mentioned on the other, leaving an intermediate space on both sidu* 

 the body, which exposes part of the gills and labial tentacles. The 

 muscular mass which bounds the anterior part of the animal's body 

 is oval, one inch three lines long, eight lines broad, and varying in 

 thickness from two to three lines : it is smooth and convex externally, 

 and hollowed out within to lodge the viscera at the base of tl 

 for the passage of which it leaves the small orifice above mentioned. 

 The margins attached to the valves are more or less irregular : Hint 

 fixed to the loose valve is the broadest, being at the ventral 

 extremity three lines in length. 



The gills have the same laminated structure as that observed in 

 other bivalves, they are broad aud short, corresponding to the form 

 of the animal ; and the lamina;, not thin compressed layers, but broad 

 and projecting but little from the sides of the visceral mass, are 

 arranged in three layers instead of two, on either side of the I 



The digestive system is accordant with the structure of the same 

 part in the other acephalous mollusks. The mouth, a transverse 

 slit, without masticatory or salivary organs, ia bounded by the upper 

 and lower labial processes which are continued in the form of two 

 transversely striated pointed tentacles on either; side : these prehensile, 

 sensitive, and probably respiratory organs measure each six lines in 

 length, and about one and a half lines in breadth. The (Esophagim, 

 after a course of two lines, dilates into a stomach, the sides of whi. -h 



are perforated by the Urge hepatic ducts. The int. Mine, after a 

 course of eight lines, forms 'a small c&cum about one lino in length. 

 The intestine, after making three close turns upon itself in the mass 

 of ova ninl hepatic follicles at the bane of the foot, paiue- in in. me- 

 diate contact with but not through the heart, and Him l~-luw tlie 

 posterior adductor, to opposite the posterior orifice of the ansl tnl>e. 

 The exterior of the intestine has an irregular honey-combed appear- 

 ance, from the close adhesion to it of the capsules of the ova. The 

 liver has the same divided follicular structure and green colour an 

 in the other Bivalves. 



The nervous system consists of a large aud conspicuous ganglion 

 situated at the posterior part of the base of the loot, just nln 

 orifice of the anal tube. Two in-rvous cords extend from this 

 iMM_-!ion, on either side the foot, to the month; other branchea radiate 

 in the opposite direction to the siphonic and addin 'tor in uncles. 



The ovary, of a gray colour, forms a mass at the dorsal aspect of 

 the body above the great adductor muacle, and extending ventral 

 on either side the oesophagus and stomach to Hie opj- > end <>f the 

 base of the foot All this mass of intestinal folds, hepatic f.>! 

 and ova was covered by a thin membrane. The lutle muscular 

 process or foot which passes through the anterior slit of the mantle 

 if but four lines long, and half a line in breadth : jt* possible use 

 may be to apply a solvent to the rock in which Hie chain' 

 i vavated. 



Mr. Broderip observes that we are left to conjecture Hie causes 



which operate to determine the animal in the choice of i fa al 



indeed it can be called choice, for most probably Claragella ir. the 



creature of circumstances, and if, soon after it exclusion from th 



i parent (when Mr. Broderip supposes it to be furnished with iU two 



FiC 1 1 part of calcareou grit rock con tain inn the fixed valve and part of the tube 

 ol Clftafflla lata ; UK. 3, external view of the right or free rulrc; fig. 4, internal 

 view of the name, ahowing the muscular impreMlonft corrcapondini: with th-i 

 of the left or fixed valve ; flg. 2, soft part* of C. Iain neen from the right aide, 

 the dermal layer of the mantle, /, being removed ; flg. A, the name Keen front 

 the left Hide, or that which In In contact with the fixed valve. The extremitlei 

 f the left labial appendage* only are exposed, no part of the (III being pro- 

 truded. A brittle i* placed in the opening of the mantle, a, anterior wall of 

 the chamber : i, dona! wall, the letter placed on the hinge of the fixed valve ; 

 , ventral wall ; rf, posterior or aiphonlo outlet ; r, tubular comtnmi 

 with a neighbouring cavity, here nent off from the interior part of the mantle ; 

 ' /, ea]eareou tubea necreted by the above proceiue* and extending Into tin 

 cavitiea oontlguoua to the throat of t in tube ; e ", a cavity communicating with 

 the anterior part of the chamber ; / , impreaaion of the posterior adductor 

 l\ it impreMi'm of the anterior adductor muacle ; A', imprCMionof the 



piillial muiMle. or third adductor;/, posterior or large adductor (the MIIK!" 

 aildiirtor of Ik .irrepond to thin, the following are miper- 



aildril ill other faiuilic* of llnalve.) ; n, the anterior, antcro-dorul, or onialler 

 -.r; A, the pnllial or antero-ventral adductor; i, the OOBVex muscular 

 iia continued over the anterior part of the body, and reducing the opening of 

 the mantle to the mall slit , through which a brltle l placed in fig. .1 (thin 

 maw in an Inordinate development of what forma the muscular margin* of the 

 mantle lobes in other Bivalves) ; *, muixular fibres of the Mphon ; ' (fig. 6), 

 the renpir.itiiry. or mgentivc xiphonle ennui; m, the anal 01 i t-. .live .i|ihonie 

 , the 'labial or hneeal np|M-nilage ; /, ll"' gill-: in tig. i the right gill 

 l een partially protruded lx mien th< 



of the ov.uy : figure* and ilex-ri|ilion from Oen, to hoe lueid ineniiiir and 

 ill.^tli.tii.ii. the lender i referml for the anatomy of the internal part) ; 

 fix. 7, anterior termination of the nheily mlie of >'. aim-la. Sow., from Mr. 

 Kowerby'a ' (ienera of llecent and Fotsil Midi..' 



