PHYSA. 227 



It is a young shell of this variety that was most pro- 

 bably figured by Donovan under the name of Helix 

 bull&oides (British Shells, t. 168. f. 2.), and of Bulla 

 fluviatilis by Dr. Turton, in his Dictionary, p. 27. 

 It is a large specimen of this variety at fig. 110., 

 and others with a rather longer spire, as if passing 

 into the next variety, which are figured by Lister, 

 t. 134., by Da Costa, t. 5. f. 6. 



The second variety, which is perhaps Physa sub- 

 opaca of Lamarck, is a larger shell, often reaching 

 3-8ths of an inch in length, which is most probably 

 described by Montagu and Turton as the adult 

 of the former variety ; for they say it sometimes 

 reaches half an inch long. It is easily known from 

 the former by the spire being produced about l-3rd 

 the length of the mouth, and formed of four or five 

 distinct convex whorls ; and it has a blunt top. In- 

 deed, by the figures of Moquin-Tandon (t. 33. f. 1. 

 16.), it is very doubtful if this variety may not be 

 the P. acuta of Draparnaud. 



This variety is called Physa rivalis by the York- 

 shire conchologists, but is quite distinct from the 

 West Indian P. rivalis described by Dr. Maton. It 

 is figured in Dr. Maton and Racket's paper (Linn. 

 Trans, xviii. t. 4. f. 1.) as Bulla fontinalis, but does 

 not agree with his description of the species, which 

 certainly belongs to the first variety. This figure 

 does not represent the inner lip sufficiently spread 

 on the body whorl. The difference in the bluntness 

 of the spire between the two varieties at first made 

 me much inclined to consider them as species ; but 

 the various specimens I have examined, and the 



Q 2 



