176 M. Desbayes' Monograph of Dentalium. 



Mollusca, and in this view of the subject he is joined by M. de Blainville, 

 who regards .its natural position as next to Patella, a striking illustration 

 of the correctness: of the views of Linne, a correctness so much the more 

 wonderful when we consider the insufficiency of his materials. 



The species anatomically examined by M. Desbayes is the Dentalium 

 Entalis, L., a species common to the English and French coasts. His 

 specimens were forwarded to him in spirit, and were consequently much 

 contracted.. The animal is conical and elongated, like the tube which it 

 inhabits, its dorsal surface corresponding with the convexity of the shell, 

 and its ventral with the concavity. It is smooth, and is obliquely trun- 

 cate in front, the centre of the truncation exhibiting a small pyramidal 

 process, which is the extremity of the foot. Posteriorly it is less muscu- 

 lar, and is usually terminated by a funnel-shaped expansion, (firm and 

 well developed in some individuals, while in others it is scarcely percep- 

 tible,) which is separated from the rest of the body by a strongly marked 

 contraction.' Above this contraction is a muscular ring, broader on the 

 ventral than on the dorsal surface, by which the animal is attached to the 

 shell ; this latter exhibiting on its inner surface, at about one-fifth of its 

 length from the posterior extremity, a corresponding horse-shoe-shaped 

 impression, the interruption being on the concave side. 



On the dorsal surface, at about one-third of its length from the anterior 

 part, a slight elevation is seen, indicating the situation of the head. Below 

 this the whole extent is occupied by two muscles on each side, which may 

 be distinctly observed through the transparent parietes of the abdomen. 

 They are symmetrically placed, flattened, and directed obliquely from 

 the lateral parts of the foot towards the dorsal surface and the posterior 

 extremity of the animal, giving origin to, and becoming confounded with, 

 the muscle of attachment. 



On the abdominal surface, also at about on€-third of its length from 

 the anterior extremity, there are visible on each side two perfectly similar 

 organs, which are deeply laciniated and of a deep brown colour, consti- 

 tuting the liver. Below- this organ, nearly the whole of the abdomen is 

 seen through its transparent parietes to be filled by granulations contained 

 in a very large ovary, and by the intestine descending in a straight line 

 and terminating at the expanded extremity of the animal in a median 

 anus. 



