86 TRACHELIPODA. 



concave beneath ; spire erect, the margin always infiected ; outer 

 lip flattened, acute, angulated, and destitute of teeth ; aperture 

 provided with a solid flat operculum, having a lateral point. 



NaviceUa elliptica. — The Oval Navicella. Plate XIII. 

 fig. 1. Smooth, shining, spotted and streaked with purple, blue» 

 or brown ; covered with an olivaceous epidermis ; spire curved, 

 prominent, extending beyond the margin. One inch long. In- 

 habits rivers in the Isle of France. 



FAMILY VII. PERISTOMIDA. 



Shell conoid or subdiscoid, with the margins of the aperture 

 united ; aperture protected by an operculum ; fluviatile, and the 

 animal respiring in water. 



Genus 60.— AMP ULL ARJ A.—Latnarck. 



Generic Character. — Shell globular, ventricose, base umbili- 

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

 margins united; outer lip acute, but not reflected; with an 

 operculum. 



Ampullaria Guyanensis. — The Guiana Ampullaria. Plate 

 XIL fig. 2. Globular, thick, with unequal longitudinal strite ; 

 covered v/ith a fuscous-brown epidermis ; inside golden-yeilow 

 Three inches in diameter. Inhabits the rivers of Guiana. 



Genus 61.— PALUDINA,— i^awiarc^. 



Generic Character. — Shell conoid ; volutions rounded or con 

 t^ex ; aperture subrotund, ovate, or oblong, angulated above ; 

 margins of outer and inner lips united, with edges acute, but 

 not reflected ; provided with an orbicular horny operculum. 



Paludina vivipara. — The Viviparous Paludina. Plate 

 XIII. fig. 3. Thin, ovate, ventricose, wrinkled longitudinally ; 

 body with three brown bands ; covered with an olivaceous epi- 

 dermis. One inch and a half long. Inhabits the rivers of 

 Europe. 



