DESCRIPTION OF SHELLS. 167 
posterior lobe slightly indicated; muscular impressions small, elongated, the 
posterior one twice the length of the other. 
This nearly resembles L. callosa of Deshayes ; the deep lunette, incurved beaks 
and muscular impressions are however striking marks. 
From the Cabinet of Mr. Edwards. 
Diplodonta dilatata. (Tab. III. fig. 16.) 
This has been separated from the genus Lucina, a genus distinguished not 
only by the teeth, which would be insufficient, as many species of Lucina have 
teeth in the hinge which are not permanent, while in others the number varies, 
but also by the form of the shell and characters of the animal. 
Cytherea lucida. (Tab. III. fig. 6.) 
Spec. Cuar.—Subtriangular, with a very circular base ; disc most convex near 
the small beaks, flattened towards the lower edge; surface polished, marked 
with few lines of growth ; lunette lanceolate ; posterior hinge-tooth in the right 
valve broad, triangular, bifid; sinus in the palleal impression elliptical. 
An elegant shining shell often marked with brown, as if stained by the remains 
of a thick epidermis; it is distinguished from C. nitidula and obliqua by the 
form of the posterior tooth in the hinge (fig. 6 a), which is narrow in all the 
varieties of both those species (fig. 13 a). 
Cytherea obliqua. (Tab. II. fig. 5.) 
There are several varieties of this shell differing in form and roughness of 
surface. The Venus tenuistriata, found at Highgate, is regularly obovate and 
gibbose, a form not common at Bracklesham. The more triangular and flatter 
form is frequent there, where also shells of an intermediate shape are very abun- 
dant. The lunette varies in form with the shell, and the least convex are gene- 
rally the smoothest ; all the varieties however may be distinguished by the hinge- 
teeth from the allied species. 
Cytherea suberycinoides. (Tab. II. fig. 15.) 
There are two varieties of this shell common at Bracklesham Bay, one furrowed, 
the other very nearly even, and therefore resembling the C. levigata of Lamarck ; 
intermediate varieties are also found. 
14, 
