UNGULINA. 



lateral, rather deep, so that, when closed, they have a 

 very regular, but thickly lenticular form. In the hinge of 

 each valve there is a single, short, bifid tooth, and besides 

 this a very small tooth in one valve; but there are no 

 lateral teeth. The pit of the ligament is oblong, placed 

 just within the anterior cardinal margin, contracted and 

 as it were divided into two portions near the center, of 

 which, that nearest the umbo receives the inner part of 

 the ligament, and the more distant part, the outer. The 

 ligament is in a great measure internal, but a small portion 

 is seen from the outside, on account of the nearly mar- 

 ginal situation of the pit. There are two oblong, muscular 

 impressions, and the impression of the muscle by which 

 the mantle is attached to the shell is entire. The Ungulinee 

 which we have seen are concentncally gi'ooved on the out- 

 side, and they have a brown horny epidermis, generally worn 

 off near the umbones, which are not eroded. We think 

 with Lamarck, that the two species he has mentioned may 

 be only accidental varieties of the same; if they are 

 distinct, the one we have represented is U. transversa. 



We are obliged to our kind friend, the Provost of 

 Eton, for the loan of the specimen from which our figure 

 is taken : we possess a specimen in a younger state, which 

 has, however, precisely the same form. 



The fi^gure given by Bosc Hist. Nat. des Coq. is U. 

 oblonga. Lam. ; in consequence of its elongated form, the 

 muscular impressions are considerably lengthened, and 

 the whole shell has much of the appejir^/nce of the human 

 n^il. 



