SPH.ERIUM. 5 



of Cyclas, which has so long received the sanction of 

 naturalists^ the principle of usage may be to some extent 

 violated, and that it may be urged,, with great reason, 

 that Linmcea and Succinea ought to give place to Nerito- 

 stoma and Auricula, which Klein had previously pro- 

 posed, as well as Physa to that of Adanson's genus 

 Bulin y but I am only in the present case following the 

 lead of experienced naturalists, and the conflict of au- 

 thorities ought to be determined by the strict rules of 

 justice. The word being derived from cr<pacp2ov, it ought 

 not to be spelt Sphcerium, as has been done by some 

 authors. 



1. SPHiERIUM CORNEUM"^, Liuue. 



Tellina cornea, Linn. Syst. Nat. ed. xii. p. 1120. Cyclas cornea, Forbes & 

 Hanley, Brit. Moll. ii. p. 113, pi. xxvii. f.3, 4, 5, 6. 



Body white, greyish, brown, or yellowish : tubes rather 

 long, slightly tinged with flesh-colour : foot somewhat longer 

 than the shell, of a faint rosy hue towards its extremity. 



Shell subglobular, nearly equilateral, compressed in front, 

 rather thin, glossy, yellowish horn-colour, with often paler 

 bands or zones which denote the periods of growth, and occa- 

 sionally having faint streaks of brown which radiate from the 

 beaks towards the front margin, shghtly but closely striate 

 transversely, and marked by obscure lines in a longitudin^d 

 direction, so as to give the surface a reticulated appearance 

 under a high magnifying power : epidermis rather thin : beaks 

 almost central : ligament short and narrow, scarcely visible on 

 the outside : inside bluish-white : hinge strong, having a double 

 cardinal tooth in each valve, besides two lateral teeth in the 

 right, and four in the left valve ; the cardinal teeth are very 

 small, but distinct ; the lateral teeth form elevated ridges or 

 plates, and are subtriangular at their extremities, those on the 

 anterior side being the largest : muscular scars or imiDressions 

 faint, owing to the thinness of the interior lining : pallial scar 

 scarcely discernible. Length 0-35. Breadth 0-45. 



Var. 1 . flavescens. Smaller and rounder ; body and shell 



* Horn-colour. 



