326 PROCEEDINGS OF THE ACADEMY 01-' [May, 



Dr. Mearns returned to Mesquite Springs along the ridge running 

 from Daniels Mt. towards our camp in Sheridan Canyon, and along 

 the wash ruiming out of this canyon. 



Dr. Mearns found the following seven species, which were deter- 

 mined by Dr. Wm. H. Dall:^ 



Patula strigosa Gould, var. concentrata Dall. [Specimens reported 

 from summit of Hacheta GTa,nde = Or eohelix hachetana.] 



Epiphragfnophora hachitana Dall [ = Sonorella hachitana]. 



Polygyra mearnsii Dall [ = Ashmunella mearnsi]. 



Thysanophora liornii Gabb. 



Holospira crossei Dall. 



Holospira hilamellata Dall. 



Holospira mearnsi Dall. 



The relationships of the Big Hachet fauna are closest with the 

 Florida and Organ ranges. Near related species of Sonorella and 

 Ashmunella inhabit these three ranges, and Sonorellas very close to 

 hachitana have been found in the Carrazolillo and Peloncillo Moun- 

 tains. The Oreohelices stand nearest to Chiricahua species. The 

 Holospiras and Vallonia are special to the range, but the other small 

 shells are common to most mountains of southern Arizona. 



Holospira is the most generally distributed snail in these moun- 

 tains. Its abstemious nature is evidently satisfied with the scanty 

 moisture supplied by the rare rains and light snow, which is said to 

 whiten the mountains for brief periods in the winter. No doubt 

 a great many colonies and other local races of Holospira remain to 

 be found. 



Holospira lives only where there is limestone. We never found 

 but one colony on igneous rock, and this was on a dyke in a limestone 

 region. They are usually found on the hot slopes, east and south, 

 where other snails are totally absent or very rare. 



The subgenus Radiocentrum of Oreohelix is represented by two 

 new species, making five now known. The new forms agree in 

 genitalia and sculpture of the embryonic shell with those already 

 known. In the large number examined^ no embryos were found, 

 so that there can be very little doubt that the species of this group 



^ Diagnoses of new mollusks from the survey of the Mexican boundary, Proc. 

 U. S. Nat. Mus., XVIII, 1895; Report on the moUusks collected by the Inter- 

 national Boundarj^ Commission of the United States and Mexico, Proc. U. S. 

 Nat. Mus., XIX, 1896. 



'' Besides dissecting several individuals each of four of the s^iecies, we have 

 pulled hundreds in cleaning the shells, without finding any embrj^os. Among 

 ordinary Oreohelices it is rather exceptional to find an individual not gravid. 



