CONCHIFERA. 
451 
mary teeth, lateral ones very conspicuous ; valves convex ; mar¬ 
gin plain. 
Lascea rubra. — The Red Lashsa. 
Plate LX XXIX. fig. 16. 
Convex, smooth, glossy, pellucid, reddish-pink. Fourth of 
an inch long. Inhabits the British seas. 
Section II.— Fluviatile. 
Shells with lateral teeth at the hinge, and covered with a spu¬ 
rious epidermis. 
Genus 26. — GALATHEA.— Lamarck. 
Generic Character. —Equivalve, subtrigonal, covered with 
a vitreous greenish epidermis; two furrowed primary teeth in the 
right valve, joined at their base; and three in the other, the in¬ 
termediate one being separate and protruding; ligament exterior, 
short, turgid, and prominent; the cordiform mark protruding in 
the centre. 
Galathea radiata. — The Rayed Galathea. 
Plate LXXXIX. fig. 20. 
Somewhat trigonal, gibbous towards the base *, covered with 
a yellowish-green thin epidermis, beneath which it is radiated 
with pale chestnut. Three and a half inches long. Inhabits the 
rivers of Ceylon. 
Genus 27.—CYRENA.— Lamarck. 
Generic Character. — Shell roundish and trigonal; turgid and 
ventricose, inequilateral, solid, with the beaks usually decorti¬ 
cated; hinge with three teeth in each valve; lateral teeth two, 
one of which is near the primary ones ; ligament exterior; a 
great part of which is inserted. 
Cyrena Jluminea .— The River Cyrena. 
Plate XC. fig. 1. 
Heart-shaped, gibbous, greenish-brown; transversely sulcated; 
variegated with white and violet in the inside. One inch long. 
Inhabits the rivers of China. 
