108 
MOLLUSCA. 
Navicella elliptica. — The Oval Navicella. 
Plate LXXXVI. 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. 
TRIBE 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. — AMPULLARIA.— Lamarck. 
Generic Character. —Shell globular, ventricose, base umbilicat- 
ed; 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 LXXXVI. fig. 2. 
Globular, thick, with unequal longitudinal striae; covered 
with a fuscous-brown epidermis ; inside golden-yellow. Three 
inches in diameter. Inhabits the rivers of Guiana. 
Genus 61. — PALUDINA.— Lamarck. 
Generic Character _Shell conoid; volutions rounded or con¬ 
vex ; 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 LXXXVI. fig. 3. 
Thin, ovate, ventricose, wrinkled longitudinally; three brown 
bands on the body, covered with an olivaceous epidermis. One 
and a half inch long. Inhabits the rivers of Europe. 
Genus 62. — VALVATA. — Lamarck. 
Generic Character. — Shell discoid or conoid; volutions cylin¬ 
drical, umbilicated; margins united and acute; operculum orbi¬ 
cular. 
