GASTROPODA 547 



Key to the genera of Pleuroceridae here described: 



Oi Aperture lengthened to form a short canal; whorls flattened. 1. PleuROCEBA 

 Ca Aperture not canaliculate ; whorls rounded 2. Goniobasis 



1. Pleurocera Rafinesque. Shell with a long, tapering spire; outer 

 lip with a projection about the middle forming a short siphonal canal; 

 surface smooth or ribbed; without umbilicus: 84 species. 



P. subulare (Lea) (Fig. 853). Shell yellowish-brown in color, with 

 a yellowish band encircling the whole just below the suture; whorls 11, 

 increasing regularly, the upper 7 with a slight revolving ridge, the 

 lower 4 rounded; length 22 mm.; width 8 mm.: upper Mississippi and 

 valley of the Great Lakes, usually on sandy or rocky bottoms. 



P. elevatum (Say) (Fig. 854). Shell yellowish or greenish in color, 

 with a yellowish band just below the suture and two purplish bands 



Fig. 853 Fig. 854 Fig. 855 



Fig. 853 — Pleurocera subulare (Baker). Fig. 854 — Pleurocera elevatum (Baker). 

 Fig. 855 — GoniobOrSis livescens (Baker). 



at the center of the whorls; whorls flattened, with revolving ridges; 

 aperture triangulate : chiefly in the drainage of the Ohio River, on sandy 

 or rocky bottoms. 



2. Goniobasis Lea. Shell rather heavy, elongated, with a long 

 and more or less pointed spire; aperture not channelled: 274 species. 



G. livescens (Menke) (Fig. 855). Shell pinkish, yellowish, or 

 greenish in color, often with two dark brown bands; surface shining, 

 wdth a slight revolving ridge in the center of all the whorls but the 

 last 2; length 20 mm.; width 9.5 mm.; whorls 7 to 9, rounded; aperture 

 ovate, purple inside; outer lip veiy convex and elongated below: valley 

 of the Great Lakes; in shallow water containing vegetation. 



G. virginica (Gmelin). Shell slender, dark brown in color; length 

 30 mm.; whorls 6, somewhat rounded: Delaware and Schuylkill Rivers; 

 common. 



Family 12. TUERITELLIDAE. 



Shell elongate, with a very long spire on which are revolving ridges; 

 no umbilicus; operculum multispiral and horny; tentacles long, with 

 eyes at their base; mantle fringed, with a siphon; aperture round, 

 without a canal: 190 species; marine. 



