394 
MOLLUSCA. 
Genus 20. — RICINULA. — Lamarck. 
Generic Character. — Shell ovate, usually tubercular or spinous 
externally; aperture longitudinal, furnished with a short re- 
curvate canal, terminated by an oblique notch; columella with 
unequal teeth; the interior of the right lip frequently obtruding 
on the aperture. 
Ricinula horrida — The Rugged Ricinula. 
Plate LXXXIV. fig. 20. 
External surface covered with strong, obtuse, black tubercles ; 
the interstices being white and transversely striated; inside of 
both lips of a rich purple ; outer lip with five triangular, grooved 
radii, between which, at their base, the margin is crenulated. 
One and a half inch long. Inhabits the East Indian seas. 
Genus 21.—CASSIS.— Lamarck. 
Generic Character. —Shell gibbous; aperture longitudinal, 
narrow, terminating in a short canal, abruptly reflected back¬ 
wards; columella transversely plicated or rugose; outer lip 
usually dentated. 
The genus consists of two subdivisions : 1. Spire with longi¬ 
tudinal varices. 2. Spire without varices. 
Cassis arelola. — The Patched Cassis. 
Plate LXXXIV. fig. 21. 
Smooth, shining, white, with square orange tesselated spots ; 
spire short and conical, with decussated striie; lower part of 
columella rugose. Two and a half inches long. Inhabits the 
Indian ocean. 
Genus 22.—C ASSIDARIA.— Lamarck. 
Generic Character. — Shell abovate, or ovate-oblong; aperture 
longitudinal, narrow, terminating in an ascending curved canal; 
outer lip marginated, or folded back at the margin; inner lip 
covering the columella, generally rough, granular, tuberculate, 
or rugose. 
Cassidaria Thyrrena. —The Thyrean Cassidaria. 
Plate LXXXIV. fig. 22. 
Ovate, transversely grooved, reddish fulvous ; volutions con- 
