8 SPH^RIID^. 



near Dublin ; and it is one of our upper tertiary fossils. 

 It is a local species. On the continent it ranges from 

 Holland to Italy. 



This fine species may be distinguished from S. corneum 

 by its much greater size, its form being oval instead of 

 globular, the strong transverse ridges, and the con- 

 spicuous ligament. The young of this are also much 

 flatter in proportion to their size. Both species occur 

 together. aS. rivicola was first indicated by Lister as 

 having been found at Doncaster. 



3. S. ova'le^, Ferussac. 



Cyclas ovalis, Fer. in Ess. Meth. 1807, pp. 128, 136. S. pallidum, Gray 

 in Ajin. N. H. ser. 2. xvii. p. 465, woodcut. 



Body milk-white : tuhes long, united nearly all the way : 

 foot tongue-shaped, very extensile and flexilDle : giUs of a 

 faint blnsh-colom. 



Shell oblong, somewhat compressed, not so equilateral as 

 the two preceding species, owing to the greater development of 

 the posterior side, thin, semitransparent, not very glossy, 

 yellowish, with sometimes a brown tint and darker zones of 

 growth, with occasionally some faint rays in the direction of 

 the lower margin, finely striate concentrically : epidermis thin : 

 anterior side rounded: posterior side trimcate, and sloping 

 towards the lower margin, which is curved and sharp : heahs 

 small, nearly central, and slightly prominent : ligament long 

 and narrow, distinctly visible on the outside: inside ashy- 

 white : liinge straight on the posterior side, and incurved on 

 the other side ; cardinal and lateral teeth arranged as in 8. 

 corneum, but the former are exceedingly small and difficult to 

 distinguish : muscular and jpallial scars very faint. L. 0-4. 

 B. 0-6. 



Habitat: Exmouth(Clark); PaddingtonCanal(J.G.J.); 

 canals and ponds in Lancashire (Darbishire) . A speci- 

 men also exists in the late Dr. Turton^s collection of 

 British shells, but without any note of the locality. 1 

 * Egg-shaped. 



