UNIVALVE MOLLUSCA, 441 
with a well-developed mantle, furnished on the inside with a band of 
tentacular filaments ; it is able to fold itself over its shell in such a 
Fig. 252.—Cyprea tigris (Linn.). Figs. 253 and 254.—Cyprza argus (Linn.). 
manner as to envelop it all round. The head is provided with two 
very long conical tentacles, each having a very large eye. The foot 
is oval, elongate, and without operculum, and is well represented in 
