PLANORBIS. 12D 



embracing about one-half the height of the hast whirl and joined by calhis. 

 Diam. one-fifth, height one-fifteenth inch. 



Interior of Oregon : Drayton. 



It is about the size of Plan, chflectus, Say, but is less depressed, the 

 whirls more cylindrical, not carinated at periphery. (^Gouhl.) 



Plunorbis veniiiculdris, GoOLD, Proc. Bost. Soc. Nat. Hist. II, 212 (1S47) ; 

 U. S. Ex. Ex. MoU. p. 112, f. 131, 131 a, 131 b (1852) ; Otia, 42. 



I have seen no specimens of this species. The original de- 

 scriptions and figures are given above. 



Planorllis deflectlis, Sat. — Shell dextral, depressed ; whirls 

 nearly five, minutely and regularly wrinkled across, wider than long with 

 a much depressed rotundity above, descending to an acute lateral edge 

 below the middle ; spire not impressed ; suture indented, but 

 not profoundly ; beneath a little concave in the middle, ex- Yis. 215. 

 hibiting one-half of each volution to the apex ; whirls flat- 

 tened, slightly rounded ; aperture declining very much, sub- C^Z^^ 

 oval, the superior portion of the labrum considerably surpass- 

 ing the inferior portion, and taking its origin a little above 

 the carina ; inferior portion of the labrum terminating on the 

 middle of the inferior surface of the penultimate whirl. 

 Greatest breadth two-fifths of an inch. 



This shell was presented to me by Dr. Bigsby, who collected 

 many specimens in the waters of the Northwest Territory. It 

 resembles the exacutus, Nob., but the aperture does not em- 

 brace so large a portion of the preceding volution, and the volutions on 

 the inferior portions of the shell are consequently more obvious and the 

 umbilicus is but slightly indented ; the upper portion of the labrum does 

 not extend so far beyond the lower portion, the aperture declines much 

 more, and the carina is less acute. It has also an afiinity for the carinatua 

 of Europe, but in addition to other differences, the aperture of that species 

 declines but little, if at all, and the carina is an elevated revolving line. 

 The aperture embraces the penultimate volution about as much as in the 

 rotundatus of Europe, to which our shell is also allied, but diflTers in its de- 

 clining aperture, and the less degree of rotundity of its whirls on their 

 upper surface. {Say.) 



Planorbis deflectns, Say, Long's Ex. II, 261, pi. xv, f. 8 (1824) : Bixney's 

 ed. p. 128, pi. Ixxiv, f. 8.— Haldeman, Mon. 25, pi. iv, f. 4^7 (1844).— 

 Gould, Invert. 207, f. 136 (1841).— Adams, Shells of Vt. 156 (1842). 

 — DeKay, N. Y. Moll. 65 (1843).— Anon. Can. Nat. II, 206, fig. 

 (1857). 



Planorbis virens, Adams, Am. Journ. Sc. [i], XXXIX, p. 274 (1840) ; Bost. 

 Jouru. Ill, 326, pi. iii, f. 15 (1840).— DeKay, N. Y. Moll, 66 (1843). 



