232 



POPULAR CONCHOLOGY. 



Villokita. Gray. — Shell (according to a figure by 

 Gray without description) thick, triangular, closed, pro- 

 vided with a strong epidermis ; and having especially strong 

 hinge teeth, lateral teeth wanting; ligament external. 

 Animal unknown. — 1 species. 



The only known species is V. cyprinoides, which is not 

 to be confounded with Cyrena cyprinoides of Quoy. The 

 locality from which it is brought appears to be unknown. 



Cyclas. Brug. (Cornea Muhlf. ; SphaBrium Gray.) 

 — Shell thin, roundish, or transverse, equi- 



valve, and inequilateral ; two small cardinal 

 teeth in each valve, one of which is folded in 

 two, but rather uncertain, lateral teeth 



lengthened transversely, and compressed; liga- Cyclas Hvicola , 

 ment exterior ; an epidermis. Animal subor- 

 bicular, its mantle freely open in front, and anteally united 

 posteriority to form a produced siphon, divided at its ex- 

 tremity into two nearly equal tubes, which, as well as the 

 margins of the mantle, are not fringed ; foot large, lingui- 

 form, very extensile ; labial palpi long, and lanceolate.* 

 — Several species ; also fossil. 



The shells of this genus are not larger than a nut ; 

 some of the species are very thin and transparent, and 

 have projecting, not eroded bosses. They inhabit rivers in 

 various parts of Europe, North America, Brazil, New 

 Holland, and there are four British species. 



Pisidium. Pfeiffer. (Pisum Megerle; Galileja Costa,) 

 — Shell equivalve, thin, usually tumid, suboval, 

 inequilateral, smooth, or concentrically stri- 

 ated ; hinge with one tooth in the right, and 

 usually two in the left valve ; also lateral 

 teeth ; ligament external, inserted at the nskitum 



. nitidum. 



shortest side. Animal suboval, with the 

 * Forbes's British Moll. 



