Fig. 744. 



494 limn.eidj:. 



fig. 135 (1841) ; Otia, 180. — Adams, Shells of Vt. 1.56 (1842). — De K.vt, N. Y. 

 Moll. 64 (1843). — Anon. Can. Nat. ii. 206, fig. (1857). 



Shell small, somewhat transparent, of a brownish-yellow color ; 

 both sides concave, the left rather more than the right, but the con- 

 cavity is there more limited by the presence of a sub-angular 

 ridge on the outer whorl ; whorls 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 

 p. kirsu- i-ovolving lines ; lines of growth very faint ; aperture sub-oval, 

 ol)lique, its diameter from side to side shorter than in the 

 opposite direction ; its plane very oblique. Long diameter, one 

 lifth of an inch ; shorter diameter, one fifteenth of an inch. 



Animal has the head slate-colored above, with a darker line along 

 each tentaculum, not originating from the eyes ; foot chestnut col- 

 ored. 



This shell was first found by Professor C. B. Adams, in Mans- 

 field, from whom I received it. I have since found it in several lo- 

 calities in Dorchester, Dedham, and Cambridge, adhering to sticks 

 in stagnant water; and it may doubtless be found in all similar 

 localities. 



This Planorbis, though in many respects it resembles in shape 

 P. deflcctus, is readily distinguished from all other American spe- 

 cies by the revolving hairy lines. It is the analogue of the Euro- 

 pean P. albus, from which it is difficult to designate any very char- 

 acteristic difference. It is, however, a thinner shell, the last whorl 

 increasing more rapidly ; and it maintains its yellowish horn color, 

 whereas P. albus assumes a spermaceti or still whiter appearance. 

 The lines, too, disappear more entirely when the epidermis is gone. 

 [Said to have been found from New England to the Saskatche- 

 wan, and in the District of Columbia. I refer it to P. albus. 



Planorbis deflectus. 



Fig. 136. 



Shell concave on the left side ; Avhiti-sh horn color ; whorls four, compressed, 

 sub-carinated ; aperture greatly declinmg. 



Planorbis drflcclus, Sat, Long's Exped. ii. 261, pi. 15, fig. 8 (1824) ; Binnet's ed. 128, 

 pi. 74, fig. 8. — Haldeman, Mon. 25, pi. 4, figs. 4-7 (1844). — Gould, Inv. 207, 

 fig. 136 (1841). — Adams, Shells of Vermont, 156 (1842). — De Kay, N. Y. MoH. 

 65 (1843). — Anon. Can. Nat. ii. 206, fig. (1857). — W. G. Binney, Smith. Inst. L. 

 and Fr. W. Shells, ii. 129, figs. 215-217 (1865). 



