94 



LAND AND FRESH WATER MOLLUSKS 



ture, which, when it has lost its hispid periostracum, can hardly be 

 distinguished from the shell which is usually called deflectus of Say. 

 This latter form, which, when in perfect condition, is fully as hairy 

 as the typical hirsutus, is apparently identical with the shell 

 which European writers catalogue under the name draparnaud^ 

 or draparnaldi of Sheppard. In its best state this has a peripheral 

 fringe of longer hairs than those elsewhere on the surface, beneath 

 which is usually, but not always, a faint peripheral keel like that of 

 P. deflectus Say, which is distinguishable, so far as the shell is con- 

 cerned, only by its less profuse and hairy periostracum. I should not 

 be at all surprised if the two were eventually shown to be extremes of 

 one specific form, especially as I have been unable to find specimens of 

 typical deflectus which do not somewhere exhibit traces of spiral stri- 

 ation like that of P. hirsutus. The identity of our American species 

 with the so-called P. albus Miiller, of Europe, I do not doubt, but 

 whether the name albus is the proper one to use for the latter is open 

 to question, and on the present occasion I prefer to use a name about 

 whose application no doubt can exist. The differences which have 

 been reported to exist between the New England and the European 

 shell are due to the comparison being made between discrepant varie- 

 ties. If a series including all varieties from many different localities 

 in Europe, be compared with a similar American series, parallels for 

 each variation will be found. 



Planorbis borealis (Loven MS.) Westerlund, after specimens fur- 

 nished by Westerlund, is merely a somewhat delicately sculptured 

 mutation of this species. 



Planorbis (Gyraulus) deflectus Say. 



Planorbis deflectus SAY, Long's Exp. Rep., n, p. 261, pi. xv, fig. 8, 1824. 

 HALDEMAN, Mon. Limn., p. 25, pi. iv, figs. 4-7, 1844 

 (N. W. Territory). 



Planorbis virens ADAMS, 1840 ; young shell. 



Planorbis obliquus DE KAY, 1843. 



Range. In America the same as that of P. hir- 

 FiG.74- Pi- t 



, . , - o/ttto. 



orbis deflectus 



s z Ottawa, Canada ! Lake of the Woods ! Great Slave 



Lake ! Dall River, Alaska, Lat. 66 N. ! Popof Island, 

 Shumagins, Alaska (Kincaid) ! 



Doubtfully distinct from the preceding species. It differs chiefly 

 from the variety draparnaudi by the feebleness or absence of the 

 hispidity of the periostracum. The deflection of the aperture and the 

 consequent form of the mouth of the shell are inconstant characters, 



