210 



branaceous margin in front, covers the anterior half, di- 

 vided longitudinally by a pellucid ftrcak: another fort of 

 fhield covers the hind part, and extends into a membran- 

 ous margin, making four lobes ; the body, on each fide, 

 runs into an angle, pointing backward, clofe to the pofle- 

 rior (liield. Beneath, the animal is divided into two parts ; 

 that before is the Snjicntaculum, behind which is the mem- 

 brane that forms the lobated end; and which is capable 

 of extending laterally, and becoming quite even; the 

 lobes being only formed by folds; on the poilerior fhield 

 above, are a few ftreaks of opaque white. 



Length of the largell examined, an inch and a half; 

 breadth one inch; length of the fheli rather more than 

 lialf an inch. 



The gizzard, or flomach, is large in proportion, of a 

 prifmatic Ihape, compofed of three tefiaccous plates, two 

 of which are of an inequi-lateral, fub-triangular form, 

 and exaflly fimilar; the other is fmaller, of an ovate- 

 oblong, inclining to lozenge-fliape, with the angles round- 

 ed ; thefe are concave on the outfide, and united together 

 by ftrong cartilages. 



The circumflance of fome of the animal inhabitants of 

 this clafs of (hells being furniflied with tellaceous ftomachs, 

 has been noticed by others, and indeed feems to have in- 

 clined fome perfons to an opinion, that no fliell can be a 

 Bulla, but where its inhabitant is pofleffed of this tefta- 



ceous organ of di<:reftion. 



. V V e 



