262 A MANUAL OF AMERICAN LAND SHELLS. 



giving the mouth a distinctly rhomboidal form in young specimens; periph- 

 eral carination almost obsolete on the last half whorl ; aperture roundedly 

 lunate, very oblique, slightly reflcxed at the umbilicus, so as to interfere 

 somewhat with its circular outline ; peristome acute, thickened within; cal- 

 lus delicate, transparent ; whorls f)^ ; suture slightly impressed, becoming 

 more distinct iu the last half whorl: surface marked with coarse transverse 

 wrinkles and faint revolving lines, the latter scarcely perceptible on the outer 

 whorl; color dull yellowish, with four brownish revolving bands, two of 

 which appear pretty constant and are situated on each side of the peripheral 

 carina, which is generally whitish ; the two remaining bands, near the suture 

 and umbilicus, respectively, fainter and less constant. Animal resembles H. 

 soUtari'i iu general form, pale, with brownish spots. Greatest diameter, IT'"^; 

 least diameter. 14™™ ; height, 11""". Young specimens only 4™"' in diameter 

 are very strongly carinated and flattened above, semi-transparent, brownish- 

 tawny in cojor, delicately marked with close revolving and transverse lines. 

 This shell is closely allied to Helix mlitaria, but is smaller, darker-colored 

 and rougher, more distinctly carinated, especially in young specimens; the 

 shell is also somewhat thicker, the umbilicus is narrower, and the lip en- 

 croaches slightly on its circular outline. Loc, Waterton Lake, Rocky Mount- 

 ains. 



HELrlCODISCUS. (See p. 74.) 



Helicodisciis fiiiibriatus, Wethekby. 



Shell light-green color, discoidal or planiform, widely umbilicate, 



Fir, -278. consistiug of about 5 whorls, very gradually increasing in 



size; aperture lunate and oblique to the axis of the shell ; 



peristome sub-acute, slightly thickened, and darker than 



the rest of the shell, the outline somewhat sinuous when 



viewed from the side of the whorl ; spire planiform, not 



rising above the body-whorl ; suture deeply and regularly 



II. fimbiiatus. impressed, umbilicus exhibiting all the volutions; whorls 



ornamented with from six to eight revolving ridges, terminating in a 



fringe-like projection of the epidermis, following this arrangement. 



Two or three of these ridges on the upper side of the body-whorl are 



often of such prominence as to give that portion of the shell a fluted 



appearance. In old shells these epidermal fringes are sometimes worn 



away, leaving the ridges upon which they stood. Greater diameter 5, 



lesser 4^""" ; height, 1^'""\ 



Helicodiseus fimiriatus, Wethekby, Journ. Cincinnati See. N. H., iv, 9 (Dec, 1881.) 

 In some specimens as many as six teeth may be observed, none of 

 which can be seen in the aperture. 



This shell, from its form and general appearance, at once reminds us 

 of R. lineatus, Say, the only other known species of tbis somewhat 

 aberrant but perfectly distinct genus. It has, however, about three 

 times the cubic capacity of its relative, and is very different in sculptur- 

 ing and ornamentation. The body-whorl is slightly deflected for a short 



