SPH^RIUM. 7 



which is another variety of the present species. Dr. 

 Baudon and M. Bourguignat both agree with me in the 

 above opinion. This species is widely distributed in 

 Europe; its northern limit being (according to Von 

 Wallenberg) Lapland^ and its southern limit being (ac- 

 cording to Philippi) Sicily. Young shells are extremely 

 flat, and might be easily mistaken for a different species. 

 This common species was first made known by our 

 countryman, the celebrated Dr. Lister, in his Treatises 

 on the history of English animals, in 1678. It is the 

 . Tellina rivalis of O. F. Miiller, and the Cyclas rivalis of 

 Draparnaud, who evidently described and figured the 

 next species {S. rivicola) as the Tellina cornea of Linne. 



2. S. Rivi'coLA*, Leach. 



Cyclas rivicola, (Leach) Lamarck, An. sans Yert. vi. p. 267 ; F. & H. ii. 

 p. Ill, pi. xxvii. f. 1, 2, and (animal) pi. Q. f. 1. 



Body yellowish-grey, or hght brown : tubes short, white, 

 and nearly of equal length : foot thick, and capable of great 

 extension, greyish-white : gills sometimes slightly tinged with 

 red. 



Shell oval, ventricose, nearly equilateral, much compressed 

 in front, rather solid, glossy, yellowish horn-colour, or ohve- 

 green, with often darker bands or zones, deeply ridged con- 

 centrically, especially towards the lower or front margin, the 

 ridges being crossed by obscure lines which radiate from the 

 beaks : epidermis rather thick : anterior side rounded : pos- 

 terior side more produced and subtruncate : heciks central, 

 small, and flattened : ligament short, prominent, and distinctly 

 visible on the outside : inside white and nacreous, with some- 

 times a yellowish tinge : hinge and teeth stronger than in /S. 

 Gorneum, but nearly of the same form : muscular and pallial 

 scars distinct. L. 0*7. B. 0*9. 



Habitat : Slow rivers and canals in the metropolitan, 

 midland, and northern counties of England, as well as 



* Inhabiting brooks. 



