256 STREPOMATIDA. 
striate, not spinose; aperture sinuate above and below, outer 
margin widely arcuately protracted. Operculum acutely ovate, 
subspiral, nucleus basal, submarginal. M. costata, Quoy. 
Famity STREPOMATID &. 
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 Melaniide have fringed mantle-margins, and the 
shells have generally a broadly rounded aperture, not produced 
at the base. 
Io, Lea. 
Syn.—Melafusus, Swains. 
Distr.—5 sp. Middle and East Tennessee, W. Virginia. J. 
spinosa, Lea (1xxi, 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 (1xxi, 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 
undoubtedly 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 Angitreme; columella 
with anterior and posterior callous deposit. 14sp. Ohio River, 
Indiana, Kentucky, Tennessee, Alabama. A. dilatata, Lea 
(1xxi, 6). 
STREPHOBASIS, Lea. (Megara [sp.],H. and A. Adams.) Shell 
like Lithasia, with retrorse canal. 9 sp. Tennessee, Alabama. 
A. curta, Hald. (1xxi, 7). 
PLEUROCERA, Rafinesque. (Ceriphasia, Swainson. Telescopella, 
Gray. Trypanostoma, Lea. Megaraand Elimia [sp.], H. and A. 
