AMPULLARIA. 



We have mentioned above the principal diiferences 

 between Ampullaria and Planorhis ; there are, however, 

 some other Genera with which it may be confounded, 

 particularly when in a fossil state, or when deprived of its 

 epidermis and operculum, and from which it is essential to 

 distinguish it ; these are Natica and Helix; it differs from 

 the first in wanting' the spiral, shelly callus which in that 

 genus is seen in the side of umbilicus, and which in some 

 instances entirely fills it up ; and from Helix in not having 

 its outer lip thickened and revolute. 



We are not acquainted with any considerable number of 

 recent species of AmpuUariae, all we have seen are from the 

 Rivers and Lakes of hot climates. Olivier ( Voj/age dans 

 U Empire Othoman^ &cO mentions one as being found in 

 the Lake Mareotis, in company with marine shells, but all 

 his endeavours to procure the living animal were fruitless : 

 we hesitate to admit into the Genus another reverse species, 

 which he calls A. carinata, abundant in a neighbouring- 

 river, but which, if we may judge from his representation, 

 has an horUy operculum, and should therefore rather be 

 considered as a Paludina. 



We are not certain that any fossil species of this Genus 

 exists : several are mentioned by Lamarck in the Annales 

 du Museum, among the fossil shells of the environs of 

 Paris ; others which are thought to be genuine Ampullarias 

 are found in the London Clay at Hordwell, and in the 

 mixed stratum between the two fresh water beds at Headen 

 Hill in the Isle of Wight. Those we have represented are 

 all recent species. 



Fig. 1 Ampullaria rugosa, with its operculum; of this species the aged shells 

 are sometimes much wrinkled. 



2 The inside of the operculum of the same. 



3 Ampullaria Cornu-arietis ( Planorbis CornU'arietis. — Lam. in EncycL 



meth. pi. 460. f. 3. 



4 Ampullaria sub car inat a: a reverse species from the Ftiver Congo: we 



have named it from the obtuse caiina which surroiiiids the umbilicus. 



