304 CYCLOSTOMATIDJE. 



More than a century ago, Guettard made known, 

 through the Academy of Sciences at Paris, the appa- 

 rently anomalous fact that a land snail was furnished 

 with an operculum. The genus Cyclostome was founded 

 by Lamarck in 1789 and reproduced in 1801, for the 

 reception of certain marine Gasteropoda which are now 

 referred to the genera Scalaria and Delphinula. But it 

 is to Draparnaud that science is indebted for the esta- 

 blishment of the genus Cyclostoma on a more correct 

 basis, although he comprised in it, besides the true 

 members of this genus, many freshwater species belong- 

 ing to the genera Paludina, Bythinia, and Hydrobia, and 

 even a species of Truncatella which is exclusively marine. 

 The present genus is restricted to those land-shells which 

 have a round mouth and a solid operculum; and the 

 structure of the animal is in strict accordance with that 

 of the shell. 



CYCLOSTOMA E'LEGANS*, Miiller. 



Nerita elegans, Mull. Verm. Hist. pt. ii. p. 177. C. elegans, F. & H. 

 iv. p. 201, pi. cxxii. f. 3. 



BODY very thick, blunt and strongly bilobed in front, 

 rounded behind, dusky greyish-brown or almost black above, 

 of a paler hue underneath, coarsely wrinkled in front and 

 finely tubercled behind : mantle semiannular, rather tumid 

 and smooth, speckled with milk-white except at the sides : 

 snout projecting beyond the rest of the body, strongly bilobed 

 in front, divided transversely by distinct wrinkles, which are 

 finely streaked with grey : tentacles dark-coloured, strongly 

 wrinkled across, with nearly hemispherical bulbs, which are 

 more transparent and clear than the tentacles : eyes placed 

 on reddish or whitish tubercles, a little behind the tentacles : 

 foot rounded in front and divided into two equal parts by a 

 longitudinal groove, very dusky, especially on the sides ; tail 

 rounded, and to a great extent covered by the operculum. 



* Elegant. 



