30 THE NAUTILUS. 



beneath. Old shells, by loss of the cuticle, have the last 1^ whorls 

 opaque white with some faint corneous or ruddy stains. Embryonic 

 shell of 2^ whorls, the first somewhat convex, first half whorl smooth, 

 next whorl having fine, close, radial thread-like stria?, last 1^ whorls, 

 having similar strice and spiral cords, becoming coarse on the last 

 half whorl. This sculpture stops abruptly at the end of the embry- 

 onic stage. Neanic and adult stages have rather fine, irregular 

 wrinkles of growth, indistinctly cut by very weak lightly impressed 

 spiral lines which are often almost obsolete. Aperture quite oblique, 

 nearly round. 



Alt. 8.6, diam. 16.3 mm.; whorls 4|. 



Genitalia as figured for 0. s. depressa and 0. elrodi, the end of the 

 penis closely resembling the latter species. Epiphallus tapers at the 

 end. Length of penis 13.6, of epiphallus 5^, of spermatheca and 

 duct 14^ mm. 



North bank of Little Thompson Creek, about 10 miles N.-W. of 

 Longmont, Colorado. About 160 living and over 100 dead shells 

 found among roots of " woodbine " in loose limestone talus, at south- 

 ern point of ridge of Niobrara Limestone, July 26, 1911, by Mr. 

 Albert Dakan. 



The strong spiral sculpture of the embryonic shell, abruptly giv- 

 ing place to oblique wrinkle-striae at the inception of the neanic 

 stage, distinguishes this species from 0. strigosa depressa (the com- 

 mon Colorado form of strigosa), to which it is related by the soft 

 anatomy. The early stages are much as in 0. yavapai, but that 

 species and its varieties differ strongly by the very short penis. 



O. gabbiana (Hemph.), from the Oquirrh Mts., differs from hen- 

 dersoni by the less strong embryonic spiral and more strongly de- 

 veloped, widely spaced spirals of the last whorl, which is carinate or 

 angular. An Oreohelix from Glenwood Springs, Colo., which has 

 been provisionally referred to gabbiana is probably a form of hen- 

 dersoni. Another form which seems referable here is from New- 

 castle, Colorado, also collected by Mr. Albert Dakan. The shells 

 are very large, alt. 14.5, diam. 24 mm., with 5^ whorls. It was 

 found on a hillside, out by thousands on a moist day. 



I should not complete this account without offering an apology to 

 Mr. Henderson for allowing the name of this species to appear in his 

 article on Oreohelix Colonies (p. 10 of the May number), in advance 

 of any published description. I had written the above account some 



