PTEROPODS. 469 
The great flappers of Hyalea tridentata are yellow, marked at 
their base with a fine violet spot. Its shell, plain above, convex 
beneath, is cloven on the side. The superior part is longer than the 
inferior, and the transverse line which unites them is furnished with 
three teeth. This shell is yellow, and nearly translucent. When 
Fig. 318. Fig. 
Fig. 317. ig 319. 
Cleodora lanceolata (Lesueur) Cleodora compressa (Eydoux Cleodora cuspidata (Rocc.). 
and Souleyet). 
the animal swims, two expansions of its mantle issue from the 
lateral clefts in the shell. 
Cleodora lanceolata is a delicate and graceful creature ; its body, 
of gelatinous appearance, has a distinct head, with its fins near the 
neck, notched in the form of a heart (Fig. 317); its posterior part 
is globulous, transparent, and luminous even in the dark. The 
animal which inhabits it sometimes shines through the shell like a 
light placed inside a lantern. This shell is triangular, as in Cleodora 
cuspidata (Fig. 319), thin, vitreous, and fragile, terminating in a long 
spine at the base. The shell in Cleodora compressa (Fig. 318) is 
elongated and very elegant in shape. 
