8 SPHJERIID^E. 



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. 8. rivicola was first indicated by Lister as 

 having been found at Doncaster. 



3. S. OVA'LE *, Fe*russac. 



Cydas ovctiis, Fer. in Ess. Meth. 1807, pp. 128, 136. 8. podlidum, 

 Gray in Ann. N. H. ser. 2. xvii. p. 465, woodcut. 



BODY milk-white : tubes long, united nearly all the way : 

 foot tongue-shaped, very extensile and flexible : gills of a 

 faint blush-colour. 



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 truncate, and 

 sloping towards the lower margin, which is curved and 

 sharp : beaks small, nearly central, and slightly prominent : 

 ligament long and narrow, distinctly visible on the outside : 

 inside ashy-white : hinge straight on the posterior side, and 

 incurved on the other side ; cardinal and lateral teeth 

 arranged as in S. corneum, but the former are exceedingly 

 small and difficult to distinguish : muscular smdpallial scars 

 very faint. L. 04. B. 0-6. 



HABITAT: Exmouth (Clark); Paddington Canal 

 (J.G. J.) ; canals and ponds in Lancashire (Darbishire). A 

 specimen also exists in the late Dr. Turton's collection 

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



* Egg-shaped. 



