GASTEOPODA 547 



Key to the genera of Pleuroceridae here described : 



Oj Aperture lengthened to form a short canal ; whorls flattened . 1. PLEUBOCEBA 

 o, Aperture not canaliculate ; whorls rounded 2. GONIOBASIS 



1. PLETJROCERA 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 siibulare (Baker). Fig. 854 Pleurocera, elevatum (Baker). 

 Fig. 855 Goniobasis 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, 

 with 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 very 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. TUBBITELLIDAE. 



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. 



