12 



LAXD AXD FKESH-WATER SHELLS OF N. A. [PART IV, 



Pleurocera. 



SPURIOUS SPECIES. 



lo nodosa, Lea. 

 Jo robiista, Lea. 

 lo variabilis, Lea. 

 lo Spilhnanii, Lea. 

 lo modesta, Lea. 

 lo viridula, Lea. 

 lo gracilis, Lea, 

 lo nobilis, Lea. 



Mr. Loa proposes to consider the above a distinct group of 

 lo, but I cannot distinguisli them from Pleurocera. The 

 longer fuse, together with the sharp lip and fragile texture of 

 most of the shells, shows them to be immature, and indeed, as 

 already stated, I have had no difficulty in several instances in 

 identifying them with species of Pleurocera, by the compar- 

 ison of specimens in various stages of growth. 



Besides tlie above, numerous species of Angitrema, etc., 

 have been referred to lo by European authors. 



Genus ANGITREMA, Haldeman. 



Angitrema, Haldejian, Cover of No. 2, Monog. Limniades, Jan., 184L 

 Potadoma (sp.), Swainson, H. & A. Adams, Genera, i, p. 299, 1854. 

 Glotella, Gray, Zool. Proc, pt. 15, p. 154, 1847. 

 lo (sp.), Lea, H. & A. Adams, Genera, i, p. 299, 1854. Chenu, Man. 



Concliyl., i, p. 290, 1859. Reeve, Monog. lo, April, 18C0. Brot, 



Syst. Cat. Mel., p. 29, 18G2. 

 Lithasia (sp.), Haldemau, H. «S; A. Adams, Genera of Recent Mollusca, 



i, p. 308, 1854. 

 Anculotus (sp.). Say, Jay, Cat. Shells, 4th edit., p. 27G, 1850. 

 Melania (sp.). Authors. 

 Juga (sp.), Chenu, Man. de Conchyl. 



Description. — Shell spinous; aperture subrhomboidal, with 

 an anterior sinus ; columella with a callous deposit anteriorly 

 and posteriorly. — Hcdd. 



Geograpldcal Distribution. — With two exceptions, the typical 

 species of this genus are contined in their geographical range 



