90 PROCEEDINGS OF THE ACADEMY OF [Feb., 



a few feet above the bed of the canyon, at and below the month of 

 Indian Creek, the shells are equally small, 12 to 13 mm. in diameter. 

 The station is deficient in herbage, more barren than higher up the 

 slopes. 



In the Box Canyon of White Tail we found a colony which differed 

 from all other lots of the White Tail region in sculpture, the striation 

 being distinct and rather sharp on the base, as in typical chiricahuana, 

 and with very weak traces of fine spiral lines. The peripheral keel 

 projects more, approaching the shape of the race from Big Emigrant 

 Canyon; otherwise the shape, size and number of whorls is as in 

 0. c. obsoleta. The conditions at this station were unfortunately not 

 noted particularly. 



No specimens of this shell were taken by Ferriss and Daniels in 1907, 

 as they did not explore the limestone ridges. In 1908 Ferriss and 

 Pomeroy found it again in Hand's Pass, over the range from White 

 Tail, in the head of Pinery Canyon. 



The embryonic shell is strongly, regularly ribbed. The shell has 

 b\ whorls, rounded, arcuate, keel nearly obsolete near the aperture 

 in mature shells; aperture nearly round, the angle formed by the 

 peripheral keel hardly perceptible. 



Alt 101 ioi lei 10 8f 



Diam 16 14+ 14+ 15+ 14 



They were found for several miles upon both sides of the trail in 

 the scattered stone upon the hillsides and around the cliffs. 



In the head of Mackey's Wash, sloping to the north, a few were 

 found, but no aged shells. The major spirals upon the under surface 

 are represented by very low, obtuse ridges. The keel becomes very 

 obtuse on the last whorl near the aperture. O. c. obsoleta was also found 

 in the head of Onion Creek (between Paradise and Jhu Canyons). 



In 1907 Mr. Ferriss passed over the wide part of the range from 

 Paradise to the mouth of Rucker Canyon and Shake Gulch, some 

 25 miles from the Cave Creek Station, and here again O. c. obsoleta 

 (fig. 13 b, c) was found in a foothill known as Limestone Mountain, 

 about ten miles in length and some 7,000 or 7,500 feet above the sea. 

 These are the largest specimens so far found, thick and rounded, 

 opaque white or pink-white and very little clouded. The wrinkles 

 w T ere coarse but obtuse upon the upper surface, the base smooth, 

 without a trace of spiral lines. 



Alt 11 10i 11 12 9 



Diam 16i 16 15+ 15+ 15 



Whorls 5+. 



