132 



LAND AND FRESH- WATER SHELLS OF N. A. [PART IL 



PlanorUs dilalntus, Gould, Invert, of Mass. 210, f. 140 (1S41) ; Otia, 182. 



— Haldemax, Mon. 23, pi. iv, f. 1(3-18 (1844).— DeKat, N. Y. Moll. 



66 (1843).— Akoxtmous, Can. Nat. II, 209, fig. (1857). 

 Planorhis dilatits, Haldejian, Mon. p. 25 (.Jan. 1844). 



Fig. 218 is a fac-simile of Gould's figures; his description is 

 copied above. 



Dr. Pfeiffer (Arch. f. Nat. 1841, p. 225) has described an Euro- 

 pean species under the same name, and in the same 3'ear (1841) 

 as Dr. Gould's species was published. The latter appeared during 

 the session of the Legislature in the spring. Prof. Haldem»n 

 (/. c.) suggests the name "dilatus,^^ should it be necessary to 

 give a new name to our shell. 



Gould (I. c.) refers to this species PL Icjis, Lea. 



It has been noticed from New England to Maryland. 



Fig. 219. 



Fig. 220. 



Plaiaorl>is albus, Mull. — Shell light yellowish-brown, concave on 

 both sides, most so on the left ; whirls three ; sur- 

 face beset with revolving lines of rigid hairs ; aper- 

 ture large, very oblique. 



State Coll. No. 82, Soc. Cab. No. 1278. 

 Shell small, somewhat transparent, of a brown- 

 ish-yellow color ; both sides concave, the left rather 

 more than the right, but the concavity is there 

 more limited by the presence of a sub-angular 

 ridge on the outer whirl ; whirls three, the outer one rapidly 

 increasing ; surface exhibiting traces of revolving lines when 

 denuded, but usually covered with a dark pigment or epider- 

 mis, bristling with rigid hairs which are arranged in close re- 

 volving lines ; lines of growth very faint ; aperture sub-oval, 

 oblique, its diameter from side to side shorter than in the oppo- 

 site direction ; its plane very oblique. Long diameter one-fifth 

 inch, short diameter one-fifteenth inch. Animal has the head slate-colored 

 above, with a darker line along each tentaculum, not originating from the 

 eyes ; foot chestnut colored. 



This shell was first found by Professor C. B. Adams, in Mansfield, from 

 whom I received it. I have since found it in several localities in Dorches- 

 ter, Dedham, and Cambridge, adhering to sticks in stagnant water ; and it 

 may doubtless be found in all similar localities. 



This PlanoHis, though in many respects it resembles in shape P. deflec- 



Fig. 221. 



