CHAPTER XLVI: THE ROUND-MOUTHED 



SNAILS 



Family CvcLOSTOMiDi^ 



Shell spiral, often depressed, not much elongated; mouth 

 round, lip simple; operculum spiral, circular; foot long; lingual 

 teeth hooked, recurved, in seven rows; mouth proboscis-like, 

 without jaws; air sac on back of neck, with open mouth; sexes 

 distinct; reproduction oviparous. 



A large family of terrestrial, air-breathing snails, resembling 

 the Littorinidae in structure. Chiefly tropical, in the eastern 

 hemisphere. 



Genus CYCLOSTOMA, Lam. 



Shell cone-shaped to globose, thin; umbilicus wide; oper- 

 culum spiral, calcareous, foot divided in middle line, sides move 

 alternately in walking; snout is used too, so locomotion is some- 

 what like the looping snail's. A large genus, with range centred 

 in Madagascar. 



Cuvier's Cyclostoma (C Cuvieranum, Petit.), the giant 

 of the genus, much depressed and thin, is strikingly angled with 

 two sharp keels, separated by a flat plane, and the whole surface 

 is finely striated. The colour is dull, a pale chocolate hue, darker 

 on the keels. The lip flares, and is thickened with an inner rim 

 of white enamel. The pit is wide and deep, all but piercing the 

 apex. These mollusks are representative of a group of species 

 of large size, and handsome form and sculpture. Diameter, 

 2^ inches. 



Habitat. — Madagascar. 



The Natica-like Cyclostoma (C. Naticoides, Pfr.) is solid, 

 polished, flesh-pink, with rounded whorls increasing to a swollen 

 body whorl, and a thickened, scarcely flaring lip. An ear-like 

 lobe of callus closes the pit. The shell lining is orange-hued. 



Habitat. — Socotra, north of Madagascar. 



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