560 UNITED STATES GEOLOGICAL SURVEY OF THE TERRITORIES. 



CERIPHASIIDiE. 



Genus GONIOBASIS, Lea. 



Synon.—Goniobasis, Lea (1862), Proceed. Acad. Nat. Sci. Philad., XIV, 262 ; and (1863) Jour. Acad. Nat. 

 Sci., V, 217; also (1865) Am. Jour. Conch., I, 118.— Tryon (1866), i&., 14; and (1873) 

 Land- and Fresh-water Shells N. Am., part IV, 138.— Meek (1866), in Conrad's Smith- 

 sonian Check-List N. Am. Eocene Invert. Fossils, 12; and (1872) in Hayden's Second 

 Ann. Report United States Geological Survey of the Territories, 298; and (1873) 

 ib., Sixth, 515. 

 Melania (part) of many authors (not of Lamarck). 



Ccriphasia (sp.), Pachychilus (sp.), Potadoma (sp.), Elimia (sp.), Hem'mnus (sp.), and Juga (sp.), of 

 authors. 



Etym.—yuvia, au angle ; fidaic, a haso 

 Examp. — G. quadricincta, Lea. 



Shell varying with the species from subovate to elongate-conoidal, or 

 subfusiform ; apex often eroded; volutions flattened, more or less convex, or 

 sometimes angular; aperture usually ovate-rhomboidal, and generally angular, 

 but without a canal below; outer lip without a slit or sinus, columella rarely 

 slightly thickened above; surface smooth, or variously ornamented with 

 revolving lines, ridges, or vertical costse, sometimes tubercular. 



Until comparatively recently, the species of this extensive genus were 

 very generally referred by American and European authorities to the genus 

 Melania. H. and A. Adams, in their valuable work on the Genera of Recent 

 Mollusca, however, separated many of them under different sections of that 

 and several allied groups, placing them in connection with foreign types, 

 belonging, according to later classifications, to different genera from all of our 

 American species, which are now, by high authorities, even ranged as a dis- 

 tinct family from the foreign Melanians. Their subgenus Elimia (under 16) 

 was largely made up of species of Goniobasis, but also included other types. 



Some of the existing species closely resemble Pleurocera of Rafmesque, 

 another American fresh-water genus, standing, as it were, between this group 

 and Io, Lea. Pleurocera, however, differs in usually having a distinctly 

 more rhombic aperture, with the outer lip more prominent below, and the 

 base generally (sometimes decidedly) more inclined to be produced in the 

 form of a short canal, than in Goniobasis, though not so much so as in Io 

 proper. 



According to Mr. Tryon's elaborate Monograph of the Strepomatidas, 

 published by the Smithsonian Institution, there are more than two hundred 

 and fifty known existing species of Goniobasis, a large proportion of which 



