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. 317- 

 Cleodora lanceolata (Lesueur). 



Fig. 318. 



Cleodora compressa (Eydoux 

 and Souleyet). 



Fig. 319. 

 Cleodora cuspidata (Rocc.). 



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. 



