85 



This shell, for Lamarck knows but of one species, V. bulloides, which 

 is fossil, approaches very near to Bulla cylindrica, or Bulla solida\ but 

 differs from the genus Bulla, in having its columella plicated. 



LV; Ampullana. A ventricose subglobose univalve, with an um- 

 bilicated base : the opening oblong and entire, with no thickening on 

 the left lip. 



The Ampullana is a river shell of the warm climates. Its spire, which 

 always projects a little, distinguishes this genus from Planorkis ; and 

 there being no thickening on the left lip, distinguishes it from Natica. 



Ampullaria patula, Lam. is Helix" mutabilis, Brand. Foss. 57. Tab. iv. 

 In Brander's figure the back is only seen ; and the patulous opening, 

 the specific characteristic, is not shown. A. sigarttina, Lam. differs 

 from the preceding, chiefly in having no umbilicus. 



From the greatest part of these shells, answering to the preceding 

 description, being marine shells, and somewhat approaching in charac- 

 ter to the genus Natica, Lamarck is disposed to think that they belong 

 to a genus not yet established. Twelve species appear to exist among 

 the fossils of the environs of Paris : A. pygmtea, A. e.rcavata, A. conica, 

 A. acuta, A. acuminata, A. spirata, A. depressa, A. canaliculata, A. patula, 

 A. sigaretina, A. crassatina, and A. hybrida. 



A. spirata, I find among my Veronese fossils ; and A. conica, and a 

 shell much resembling A. rugosa, I have found among the shells of the 

 Essex cliff. 



LVI. Planorbis. A discoidal univalve. The spire depressed, hardly 

 at all prominent, the turns conspicuous on both sides. The opening 

 entire and oblong; the margin never reflected. 



The shells of this genus are fresh-water shells: their inferior face is 

 known, by its being more sunk in than the upper; and from the gra- 

 dual diminution of the turns towards the centre, forming a funnel- 

 formed cavity. 



From the original delicacy of structure of these shells, from the cir- 



