56 EOCENE MOLLUSCA. 
extremity of the siphonal region, and ornamented with diverging ribs; dorsal margin 
straight, ventral margin slightly curved. 
Length.—9 to 11 inches. 
Localities Highgate, Whetstone, Chalk Farm (Wetherell), Sheppey, Newnham 
(Prestwich), Bognor, (Hdwards). 
Our shell is ornamented with about sixteen or eighteen rather elevated rays or coste, 

slightly imbricated, and sometimes undulating, with occasionally a small intermediate ray. 
This species appears to have possessed a habit similar to that sometimes seen in 
species of Modiola ; two or three specimens are found together, the one enveloping the 
other. A young fry probably occupies the shell of its parent, which it has never left, and 
perhaps grows to its full size where it was born, filling entirely with its own shell the one 
previously occupied by the mother. Mr. Edwards’ specimen shows this intimate union 
of three individuals, each as nearly as possible of the same size. An imperfect specimen 
of this species in the Museum of the Geological Society indicates a length of twelve 
inches 
2. Pinna arcuata, J. Sowerby. Tab. XI, fig. 8. 
Pinna arcuatTa. J. Sow. Min. Conch., t. 313, fig. 3. 
— — Prestwich. Journ. Geol. Soc., 1847, p. 405. 
= — Morris. Catal. Brit. Foss., p. 180, 1854. 
— — D Orbigny. Prod. de Paléont., t. 11, p. 391, 1850. 
“ Nearly equilateral, ventricose, finely ribbed, arched.” 
Longest diameter, $ths of an inch. 
Locality —Nighgate (J. Sowerby). 
“Nearly as deep as long; the hinge-line is gently curved; the opposite edge much 
arched ; in other respects, this strongly resembles the last.” 
“ Having several specimens of this arched Pinna from Highgate, exactly alike as well 
in curvature as in size, I cannot but consider it a distinct species. It appears to be quite 
different from P. crxcurva, Linn. : it occurs in Septaria.” (Sowerby). 
The figure above referred to, and the description, are taken from ‘ Min. Conch.’ 
3. Pryna MARGARITACEA, Lamarck. Tab. XI, fig. 9. 
PINNA MARGARITACEA. Zam. Ann. du Mus., t. vi, p. 218, and t. ix, t. 17, fig. 8. 
_— _— Defrance. Dict. des Scien. Nat., t. 41, p. 71. 
— — Desh. Coq. Fos. des Env. de Par., t. i, p. 280, pl. 41, fig. 15. 
— -— Id. An. sans Vert. du Bassin de Par., t. 1i, p. 35, 1860. 
= = Nyst. Coq. Foss. Belg., p. 274, pl. 20, fig. 9. 
_ — J. Sow. in Dixon’s Geol. of Sussex, pp. 94, 117, 172, 226. 
= — Morris. Catal. Brit. Foss.,p.180. 1854. 
