BIVALVIA. 71 



This is an extremely delicate shell, and very rare; a few specimens, however, are 

 quite perfect, and will bear a fair comparison. The shell to which it most nearly 

 approaches is the common British species, M. marmorata, but it differs essentially in several 

 characters ; these have been pointed out by M. Deshayes, the founder of the present 

 species. The British fossil appears to correspond with the French shell, so far as depen- 

 dence can be placed upon figures and descriptions, and I have not been able to see a 

 specimen of the latter. The stria) on the pedal region arc very large or broad, becoming 

 narrower towards the central smooth space, where they terminate with two or three very 

 fine lines ; the radiations on the siphonal region arc not so broad ; all the rays are flat, 

 with narrow depressions between them. The smooth or naked central space occupies 

 about one third of the surface of the shell, and the lines of growth are here distinctly 

 visible, sometimes raised almost to ridges. The rays on both regions of the French shell 

 are represented of the same size, but they are not so on ours. 



One of Mr. Edwards's specimens has enclosed within its valves no less than three 

 others, enveloping one another; one of these enveloped specimens is in a reversed 

 position. 



15. Modiola simplex, /. Soiverbg. Tab. XII, fig. 7, a, b. 



Modiola simplex. /. Soiv., in Dixon's Geo], of Suss., pp. 117, 225, t. 14, fig. 16, 1850. 



— — Morris. Catal. Brit. Foss., p. 212, 185 1. 



Spec. Char. M. testa tenui, clongatd, obtuse cuneata vet subtrapeziformi, laevigata; 

 wmbonibus minutis, depressis, subteni/inalibus ; pedi-regione brevi, contractu; siphoni- 

 regione tat lore, compressd ; margine dor sail recta, extensd. 



Shell thin, elongated, obtusely wedge-shaped or obtusely trapeziform, smooth ; 

 beaks small, depressed, nearly terminal ; pedal region very small and narrow ; siphonal 

 region broad and compressed ; dorsal margin straight and extended. 



Length, If inch. 



Localities. Bognor and Heme Bay (LJdivards). 



Mr. Sowerby says, '* It is like M. depressa of ' Min. Conch./ but is more pointed." 



There appears also to be a little difference in outline ; the dorsal margin is less curved 

 and more extended, and the siphonal region is rather more compressed. 



16. Modiola subcarinata, Lamarck. Tab. XII, fig. 9. 



Modiola subcarinata. Lain. Ann. du Mus., t. vi, p. 222 ; and t. ix, pi. 17, fig. 10 a, b. 



— — J. Sowerby. Min. Conch., pi. 210, fig. 1, 1818. 



— — Desk. Coq. Foss. des Env. de Par., t. i, p. 256, pi. 39, figs. 4, 5. 



— — Morris. Catal. Brit. Foss., p, 212, 1854. 



— — Desk. An. s. Vert, dn Bassin de Par., t. ii, p. 25, 1860. 

 Mytilus — If Arcldac. Foss. du gr. numm. dans Mem. de la Soc. Geol. dt 



Fr,, 2 se'r., t. Hi, pp. 433, 453, 1850. 



