304 CYCLOSTOMATIDiE. 



More than a centmy ago^ Guettard made known, 

 through the Academy of Sciences at Paris, the appa- 

 rently anomalous fact that a land-snail was fiu-nished 

 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 ekgans, 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 fi'ont 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 bdobed in front, divided trans- 

 versely 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 Httle 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 



