1905.] NATURAL SCIENCES OF PHILADELPHIA. 283 



I have partially examine 1 the internal anatomy of one of the speci- 

 mens from Beiilah. The penis (PI. XIX, fig. 9) is bent in the middle, 

 the lower half a little swollen, with muscular walls, the upper half 

 slightly smaller, softer. There is a very small apical papilla, and the 

 retractor muscle is inserted at the apex of the penis and root of the 

 epiphallus. The epijshallus is large, shorter than the penis, and the 

 vas deferens enters at the side, not the center of the apex. 



The radula has 19.1.19 teeth, similar to those of 0. yavapai. On the 

 fifth or sixth teeth the ectocone is developed. Marginals bicuspid, as 

 usual. 



Subgenus RADIOCENTRUM nov. 



Oreohelices with an embryonic shell of H radially ribbed whorls, 

 spiral strise in the intervals between ribs excessively weak or wanting. 

 Penis rather short, with a hollow dilation at the distal end. Epiphallus 

 club-shaped, as long as the penis, the retractor inserted near its base. 

 Type 0. chiricahuana Pils. 



This group differs from Orcohelix by the smaller number of embryonic 

 whorls and their different sculpture, and in the somewhat different 

 structure of the penis. It includes at present three species: 0. chiri- 

 cahuana, 0. clappi and 0. avalonensis. 



The genitalia are similar in the two species examined, the only 

 difference being in the shape of the distal end of the penis, and in the 

 absolute dimensions. The pallial organs of 0. clappi do not differ from 

 those described above for Oreohelix strigosa. 



Key to Species of Radiocentrum. 



a. — Shell bluntly subangular or almost rounded at the periphery; cov- 

 ered with a green or olive cuticle, largely worn from old shells. 



Alt. 8.5 to 9.7, diam. 15 mm., 0. clappi Ferriss. 



a'. — Shell carinated; earthy, without perceptible cuticle. 



b. — "Whorls 44, granulated above and below, the last one wide; 

 aperture large. Alt. 6, diam. 11 mm." (Hemphill). I 



0. avalonensis Hemphill, 

 6'. — Whorls 5, striated but not granulated, slowly widening; 

 aperture small. Alt. 6.5, diam. 11 mm., 



0. chiricahuana Pils. 



Oreohelix chiricahuana n. sp. PI. XI, figs, l, 2, 3. 



The shell is depressed, the altitude about .6 of the diameter, about 

 equally convex above and below the peripheral keel. Umbilicus rather 

 well-like, slowly contracting, and contained five or six times in the 

 diameter of the shell. Whitish, with an indistinct gray band near 



