102 EOCENE MOLLUSCA. 



striae or depressed riblets decussated by limes of growth ; hinge-area broad, with few teeth, 

 lateral denticles striated. 



Diameter, 2 inches. 



Localities. Heme Bay (Edwards), Upnor {Preshoich). 



France: Les environs de Soissons, pres d'Etampes, &c. (Desk.). 



The most distinguishing character in this species is a prominent or rather recurved 

 umbo, somewhat resembling the beak of a Terebratula, which, I presume, suggested the 

 name to Lamarck. 



Fig. 10, Tab. XVI, represents a shell that was some years since obligingly given to me 

 by Professor Morris, and it had the locality of Ilford attached to it, but that gentleman is 

 now unable to state from what bed it was derived. It was accompanied by a Cytkerea from 

 the same locality, and this latter species I have since obtained from the Woolwich beds 

 underlying the London Clay, reached in a well-sinking at Romford. There is therefore 

 every probability that our specimen came from the same bed at Ilford. I am unable ta 

 assign this specimen to any species known to me, unless it might perhaps be referred to 

 brevirostris, but with which it does not strictly accord. P. poli/morphus also much 

 resembles it. 



A shell from the Paris Basin has been figured and described under the name P.pauci- 

 dentatus (Desh.), 'An. sans Vert, du Bass, de Par.,' t. i, p. 852, pi. 73, f. lfi, 17, which 

 has the locality of Woolwich attached to the description. I have not been able to find 

 any British specimen entitled to that distinction. 



LIMOPSIS, Sassi, 1827. 



Gen. Char. Shell orbicular or slightly oblique, convex or lenticular, equivalved, sub- 

 equilateral, closed ; hinge with two slightly curved and slightly unequal series of projecting 

 and interlocking teeth ; umbones distant ; connexus ligamental, bipartite, one portion 

 inserted in a triangular cavity immediately beneath the umbo ; impression of the mantle 

 entire. 



The animal of one species of this genus [L. aurita) has lately been obtained in the 

 seas of North Britain by Mr. Jeffreys, the account of which has been published in the ' Ann. 

 and Mag. Nat. Hist.,' 1862, and he says " the body is of a milk-white colour. The mantle 

 is open at every part except behind ; it has no folds or tubes, and its edges are thickened 

 and furnished with papilliform glands. The foot is large in proportion to the rest of the 

 body, and it is shaped like a tobacconist's knife ; it can, in all probability, form a suboval 

 disc at the central portion, as in Pectuncutus." It so much resembles that genus that 

 the only distinction on which a separation can be founded is the triangular fossette in the 

 area for connexus, and this cannot be considered a very important one, as it is present 

 upon the young shell of Pectuncutus decussatus. 



