FAMILY 3. CYCLOSTOMACEA. 95 
CYCLOSTOMA, Lamarck. 
Testa turbinata, varia, nunc turriculata, nune globosa, nunc trochifor- 
mis, nune discoidea, anfractibus rotundatis, umbilicum szpissime 
amplum formantibus ; apertura rotunda, marginibus plerumque con- 
nexis ; labro expanso, reflexo, fimbria interdum ornato. Opercu- 
lum vel corneum, vel calcareum, semper spirale. 
The genus Cyclostoma was originally intended by Lamarck, in literal 
accordance with its title, to include all gasteropodous mollusks whose 
shells were distinguished by their having a circular mouth or aperture. 
This arrangement, however, was but lightly appreciated ; for, in follow- 
ing so general a character, the terrestrial and marine kinds were indis- 
criminately assembled together; the Turbo delphinus of Linnzus being 
regarded as the type of the genus. Draparnaud appears to have been 
the first to note the manifest impropriety of associating in the same ge- 
neric division, animals differing so materially in their organization and 
habits. The particular attention that was given by this author to the 
land and freshwater mollusks suggested to him the necessity of keeping 
them separated, and this improved method of arrangement was then re- 
cognized by Lamarck in the formation of certain new genera, which he 
distinguished accordingly, Delphinula, Scalaria, Paludina, Valvata, ex. gr. 
If it were not that those species which are now reserved as Cyclosto- 
mata are terrestrial, air-breathing mollusks, the rotundity of the whorls, 
together with the peculiarity of their being furnished with an operculum, 
would still entitle them to a place in the family of the Turbinacea. And 
even now the policy of separating the land from the sea mollusks is ques- 
tioned by some authors: De Blainville, for example, appears to give little 
or no attention to this important difference in the respiratory system ; the 
genera Turbo and Cyclostoma being arranged by this author in one and the 
same family, Cricostomata. 
