1918.] NATURAL SCIENCES OF PHILADELPHIA. 301 



The largest specimen from the type locaUty measures 17.2x28.6 

 mm.; the smallest, 12.5x23.2 mm.; very few are under 25 mm. diam- 

 eter. The largest shell in the lot from the west side of Hog Canyon 

 measures 17.5x30 mm. 



The Tortillitas are arid mountains without forest. 



Sonorella rinconensis Pils. & Ferr. 



Sonorclla rinconensis Pilsbry & Ferriss, Proc. A. N.S. Phila. 1909, p. 517, 

 fig. 1, pi. 22, fig.?. 1-3, 5, 7.^ 



Rincon range: Rincon Peak and Wrong Mountain; Mt. Mica, 

 only those from Rincon Peak dissected. This species was not en- 

 countered in the localities visited in 1917. It inhabits elevations 

 above 7,500 ft., occurring in granitic rocks. 



Thysanophora hornii (Gabb). 



Santa Catalina Mountains : Stations 3 and 9, near mouth of Sabino 

 Canyon, 4,500 ft. Station 13, mouth of Bear Canyon, 4,500 ft. 

 Station 40, Alder Springs, 8,000 ft. Southern foothills of Rincon 

 Mountains near the cave, Station 191 (1918). Gahuro Mountains. 



Thysanophora ingersoUi (Blaud). 



Santa Catalina Mountains: Mt. Lemon at Stations C, 19, 31, 

 34, 37, etc., at 9,000 to 9,500 ft. 



ENDODONTID^. 

 Gonyodiscus cronkhitei (Nc.) 



Santa Catalina Mountains: Station 21, Desert Laboratory 

 Plantation, 8,500 ft. Soldier Camp. Bear Wallow. Around Mt. 

 Lemon at Station C, spring on west side; Station 19, Congdon's 

 Cabin; Station 28, marshy spring; Station 37; Station 22, old Lemon 

 trail; Station 31, aspens, new trail; Station 34, 9,000 to 9,500 ft. 



Rincon Mountains: Spud Rock and Catalina saddle. 



Radiodiscus millecostatus Pils. & Ferr. 



Santa Catalina Mountains: Environs of Mt. Lemon, Stations C, 

 19, 28, 30, 31, 34, 37 and some others, at elevation of 7,000 to 

 9,500 ft. Bear Wallow. Kellogg Peak. Generally distributed and 

 locally very abundant, especially in the aspen zone. 



Helicodiscus arizonensis P. & F. 



Santa Catalina Mountains: Station 1, near weir, Sabino Canyon, 

 4,500 ft. Station 27, Bear Wallow. Marble Peak at Station 25, 

 8,500 ft., and Station 26, 8,000 ft. Rincon Mountains : Spud Rock. 

 Galiuro Mountains, Station 24 (1917). 



* The reference to figures " 1-4, 7" as given in our paper was incorrect. 



