Mr. J. Gwyn Jeffreys on some British Fresliioater Shells. 341 



sent to Dr. A. S. Packard by Dr. Liitken, under the name of 

 B. paludosus^ Miiller. The latter appears to be quite distinct, 

 to judge from the figures ; it is represented as having appen- 

 dages between the claspers, and very slender, linear caudal 

 appendages. In the form of the egg-pouch and the serration 

 of the first joint of the claspers it is similar. 



This species is very closely allied to B. arcticus ; and when 

 a larger series of specimens can be examined, it may prove to 

 be only a local variety ; but the specimens studied show dif- 

 ferences that seem to warrant their separation. 



XL. — On some British Freshwater Shells. 

 By J. Gwyn Jeffreys, F.R.S. 



I LATELY received from Mr. Thomas Kogers, an active and 

 enthusiastic naturalist at Manchester, specimens of a small 

 Planorbis, for my opinion. He discovered them in the Bolton 

 Canal. They proved to belong to a species new to Europe, 

 viz. the P. dilatatus of Gould (P. lens^ Lea) , which was origi- 

 nally found near Cincinnati, and inhabits an extensive tract 

 of the United States. The shell is about the same size as P. 

 nautileus, which may be considered its nearest ally ; but it has 

 one whorl less, the periphery is angulated, the underside is 

 remarkably gibbous, the mouth is very large, squarish, and 

 scarcely oblique, the outer lip is expanded (" so as to make it 

 trumpet-shaped," Gould), and the umbilicus is abruptly con- 

 tracted, small, and deep. Some of the Manchester specimens 

 are more or less distinctly, though microscopically, striated in 

 the direction of the spire. The following is a description of 

 the animal or soft parts : — 



Bod^ dark grey, often with a slight orange tint, closely and 

 minutely speckled with flake-white : mantle thick, lining 

 the mouth of the shell : head large and tumid : mouth fur- 

 nished with broad lobular lips : tentacles cylindrical and 

 extensile, widely diverging, broad and triangular at the 

 base ; the sheath or outer part is gelatinous, and the core or 

 inner part is of a much darker colour and apparently greater 

 consistence ; tips rounded : ei/es sessile, on the inner base of 

 the tentacles : foot oblong, squarish in front, and bluntly 

 pointed behind : verge curved, on the left-hand or umbilical 

 side of the shell. The spawn is arranged in an irregular 

 mass containing about a dozen membranous capsules, each 

 of which has a yellowish yolk or vitellus in the centre. 



It is active, and occasionally creeps, like many other aquatic 



