TRACHELIPODA. 99 



Plate XII. fig. 14. Shell small, oval; back convex, smooth, 

 white, variously speckled with red, black, or dark brown ; 

 spire inclined, lateral; lip slightly denticulate. One-third 

 of an inch long. Inhabits the rivers and streams of Europe. 



j Genus 59.— NAVICELLA.— Zamarc^. 



! 



Generic Character. — Shell elliptical or oblong, convex 



above, concave beneath; spire lowered to the margin; inner 



I lip flattened, acute, narrow, and destitute of teeth; aperture 



' provided with a solid flat operculum, having a lateral acute 



I point. 



I Navicella elUptica. — The Oval Navicella. Plate 

 j XIII. tig. 1. Smooth, shining, spotted and streaked with 

 j purple, blue, or brown ; covered with an olivaceous epider- 

 mis; spire curved, prominent, extending beyond the margin. 

 I One inch long. Inhabits rivers in the Isle of France, India, 

 i and the Moluccas. 



FAMILY VII. PERISTOMIDA. 



Shell conoid or subdiscoid, with the margins of the aper- 

 ture united; aperture protected by an operculum; fluviatile, 

 and the animal respiring water. 



Genus 60.— AMPULLARIA.—Za/narc^. 



Generic Character. — Shell globular, ventricose, umbili- 

 cated; inner lip without a callosity; aperture oblong, entire ; 

 margins united ; outer lip acute, but not reflected ; an oper- 

 culum, 



Ampullaria Guyanensis. — The Guiana Ampullaria. 

 Plate XII, fi^g. 2. Globular, thick, with unequal longi- 

 tudinal striae ; covered with a fuscous-brown epidermis ; 

 inside golden-yellow. Three inches in diameter. Inhabits 

 the rivers of Guiana. 



Genus 61 P ALUDIN A. —Zamarc/i. 



Generic Character. — Shell conoid ; volutions rounded or 



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