82 



PROCEEDINGS OF THE ACADEMY OF 



[Feb., 



3. Onion Creek Form. — This form resembles the second form from 

 Cave Creek and 0. c. emigrans in shape. Compared with 0. clappi the 

 whorls are natter, less convex, sutures not so deep. The last whorl 

 invariably falls to the aperture further below the angle of the preceding 

 whorl, and the peripheral angle continues strong as far as the lip-edge. 



Cuticle thin, persistent, not ragged or broken, light greenish olive, 

 lustreless, with occasional dark oblique lines, which, near the aperture, 

 become crowded. It is seldom banded spirally and then the bands 

 are indistinct, obscure brown and transparent. The growth-striae are 

 sharper, more distinct than in Cave Creek clappi. It is very densely 

 and distinctly striated, spirally. Oblique waved riblets and traces of 

 spiral wreaths on the base, as in 0. c. emigrans, are shown in young 

 shells, and sometimes upon the penultimate whorl of the mature 

 shell within the aperture, but seldom pei'sistent upon the exterior. 

 There are nearly 5 whorls. The aperture is pear-shaped, its upper 

 margin nearly straight (consequent upon the flatness of the whorls); 



Fig. S. — Oreohelix clappi, lower Cave Creek, Station 12. 



not arched, as in typical 0. clappi. The smaller shells measure about 

 8.8 X 15 mm.; the largest in about one hundred specimens measure: 



Alt, 1(H, diam. 17^ mm. 



10i, 

 10*, 



10, 



m, 



17 



17 

 17 

 16 



Found at the head of the main fork of Onion Creek, a branch of 

 Turkey Creek, on the north side of the range. It was found in a shat- 

 tered column of quartzite in company with Ashmunella, Sonorella, 

 Succinea avara and two rattle-snakes, Crotalus pricei and C. lepidus. 

 Oreohelix chiricahuana dwelt in the limestone over the ridge, less than 

 a half mile distant. The station is about 4 miles from the locality 

 of 0. clappi and 16 from that of 0. c. emigrans, and upon a direct 



