CYCLADID^E 7 



TRIBE VI. CTCLOSTOMIDIJE. 



Animal With a spiral body; two tentaculce with eyes at their 



inner bases; foot ovate. Terrestrial. 

 Shell Ovate and turreted, strong; mouth oval ; operculum 



consisting of several whorls. It includes, according to 



the present arrangement, two genera Cyclostoma and 



Acme. 



CYCLADID^E. 



CYCLAS. Brugiere. 



Shell Subglobose, equivalved, more or less finely stri- 

 ated ; cardinal teeth small, sometimes undis- 

 tinguishable, one in the right and two in the left 

 valve. Lateral teeth developed transversely, dis- 

 tinguished from the Pisidia by being larger, 

 rounder, and more equilateral. 



Animal Mantle produced behind forming a siphon, 

 which is divided into two nearly equal tubes. 



C. RIVICOLA. Leach. PL I, fig. 2. 



Shell subglobose, striated concentrically ; umbones obtuse; cardinal 

 ligaments distinct. 



Tellina cornea ; var. B. Linn. Cyclas cornea, Drap. 



This is the largest of British Cycladidae. Its form is 

 roundish, oval, and very slightly inequilateral. It is 

 comparatively strong and opaque. The valves are 

 covered more or less closely with concentric striae, 

 which are less distinct on the umbones. The epidermis 

 is glossy and of a brownish green, with darker zones ; 

 the umbones have generally a yellow tinge. Interior 

 of a bluish white colour. 



Ordinary length five-sixths of an inch, and breadth 

 two-thirds of an inch. 



The tubes of the animal slightly tinged with brown, 

 foot and mantle white. 



Hob. The river Thames in considerable abundance; 

 it has also been found in the Trent, New River, Lea, 



