256 STREPOMATID^. 



striate, not spinose ; aperture sinuate above and below, outer 

 margin widely arcuately protracted. Operculum acutelj^ ovate, 

 subspiral, nucleus basal, submarginal. M.costata^ Quoy. 



Family STRBPOMATIDvE. 



Shell turreted, or ovate, smooth or variously sculptured, 

 covered with an olivaceous epidermis ; aperture angulated or 

 channeled in front. Operculum subspiral. 



Animal with plain (not fringed) mantle-margin. Oviparous. 

 Dentition (xl, 27). 



Except two or three West Indian species, the distribution of 

 the family, numbering about 500 species, is confined to the United 

 States, and principally to the upper waters of the streams taking 

 their rise in the mountains of the middle southern region. 



The oriental Melaniidae have fringed mantle-margins, and the 

 shells have generallj'^ a broadly rounded aperture, not produced 

 at the base. 



lo. Lea. 



Syn. — Melafusus, Swains. 



IHstr. — 5 sp. Middle and East Tennessee, W. Virginia. I. 

 spinoaa, Lea (Ixxi, 3, 4). 



Shell fusiform,usually nodulous, with elevated spire; aperture 

 produced anteriorly into a narrow, twisted canal; columella 

 smooth, concave. 



Angitrema, Haldeman. 



Syn. — Potadoma (part) Swains. Glotella, Gray. Juga (sp.), 

 Chenu. Meseschiza, Lea. 



Distr — 12 sp. Indiana, Tennessee, Northern Alabama. A. 

 Duttoniana, Lea (Ixxi, 5). 



Shell spinous ; aperture subrhomboidal, with an anterior short 

 canal; columella with a callous deposit anteriorly and posteriorly. 

 Meseschiza is founded upon young specimens of A. armigera, 

 Say, in which the growth of the outer lip has been interfered 

 with at its periphery, causing a" seam and slight sinus ; it is 

 undoubtedl}^ monstrous. 



LiTHASiA, Haldeman. (Megara [sp.], H. and A. Adams.) Shell 

 ovately fusiform or oval, small, smooth ; aperture not so dis- 

 tinctly channeled in front as in the typical Angitremge ; columella 

 with anterior and posterior callous deposit. 14 sp. Ohio River, 

 Indiana, Kentucky, Tennessee, Alabama. A. dilatata. Lea 

 (Ixxi, 6). 



STREPHOBASis, Lea. (Megara [sp.],H. and A, Adams.) Shell 

 like Lithasia, with retrorse canal. 9 sp. Tennessee, Alabama. 

 A. ciiWa, Hald. (Ixxi, 1). 



PLEUROCERA, Rafiuesque. (Ceriphasia,Swainson. Telescopellu, 

 Gra3^ Trypanostoma, Lea. Megara and Elimia [sp.J, H. and A. 



