NORTH-CAROLINA GEOLOGICAL SURVEY. 273 



FAMILY HELICTDAE LAND-SHELLS. HELIX TRIDENTATA. 



(Fig. 183.) 



Shell depressed, or flattened, convex ; whirls, four and ob- 

 liquely wrinkled ; aperture contracted and furnished with two 

 teeth on the outer lip, and one upon the inner lip ; the latter 

 is curved. 



FIG. 186. FIG. 185. FIG. 184. FIG. 183. 



H. LABYRINTHICA. (Fig. 184.) 



Shell small and of a conical form ; whirls, six and marked 

 with oblique lines of growth ; lip reflexed ; inner lip furnished 

 with a single tooth extending within the shell. 



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FAMILY LIMNEIDAE. FRESH-WATER SHELLS. PLANORBIS BICARI- 



NATUS. (Fig. 185.) 



Shell deeply concave on both sides ; whirls, three ; carina- 

 ted on both sides ; lip on the left extending beyond the plane 

 of the preceding whirl. 



This fresh water shell is rare in the miocene beds of the 

 Cape Fear. 



FAMILY PALUDINIDAE. 



This family embraces certain gasteropods, most of which 

 live in fresh water, as lakes, ponds and rivers. The form of 

 their shells is conical or globose, covered with a thick green 

 epidermis. The aperture is rounded and the whirls convex ; ' 

 peristome continuous. 



t 



PALUDINA SUBGLOBOSA. N. S. (Fig. 186.) 



Shell rather thin, turbinated ; whirls, four, rounded or con- 

 vex, short ; aperture rounded ; third whirl marked by four or 

 five spiral obsolete lines. It has a close resemblance to 

 Gould's and Halderman's genus Amnicola. 



Miocene of Cape Fear, but it is by no means a common 

 shell. 



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