MOLLUSCA. 459 



B. Aperture of the shell destitute of a thickened margin. 

 There is in this group no certain indication of maturity 

 or stationary growth. 



1. Mouth ufthe Shell at the Pillar entire. 



23. ViTKiNA. — Margin of the shield double. 



The upper fold of the shield is divided into several lobes, 

 which are capable of being reflected over the surface of the 

 shell. The shell itself is not capable of containing the whole 

 body of the animal. The Helix pellucida of Mulleh is 

 the type of the genus. It is a common British species, and 

 was hastily regarded by Montagu as the fry of the Helix 

 lucida *. 



2. Mouth of the Shell at the Pillar effuse. 



24. SucciNEA. — Termination of the pillar rounded. 

 The mouth is large in proportion to the size of the shell, 



with the outer-lip thin, and the pillar attenuated. We are 

 at a loss to account for the conduct of Lamark in substi- 

 tuting a new name for this genus, without any apparent rea- 

 son, and thus adding to the synonimes with which the 

 science is already oppressed. The name first employed by 

 Drapaknaud, indicates one of the most striking characters 

 of the type of the genus ; whereas the term AmpMbulina, 

 used by Lamark, is founded on a mistake, and is apt to 

 mislead. The Helix succinea (the type of the genus), 

 although found in damp places, is not amphibious. It 

 never enters the water voluntarily. Indeed Muller says, 

 " Sponte in aquam descendere nunquam vidi, e contra 

 quoties eum aquae immisi, confestim egrediebatur.'" The 

 same remark is made by Montagu, and we have often 

 witnessed its truth. 



25. AcHATiNA. — The termination of the pillar truncated. 



* A figure of this species is given in Plate IV. f. 1. 



