342 PROCEEDINGS OF THE ACADEMY OF [May, 



northern New Mexico, north to British America, and in its greatest 

 amplitude from the Mississippi Eiver (pleistocene) to eastern Wash- 

 ington. The most widely spread species is 0. cooperi, with 0. strigosa 

 depressa next. 0. haydeni also is spread over a considerable though 

 much smaller area. Most of the other species and races are rela- 

 tively local in distribution, and many are known from but one or a 

 few contiguous colonies. 



Oreohelix cooperi still occurs from the Black Hills to Montana and 

 Idaho, and from Assiniboia to the southern third of New Mexico 

 and Arizona. Its range was formerly wider, as it is not uncommon 

 in the loess of eastern Iowa. Its presence there indicates a drier 

 and cooler summer climate than that of eastern Iowa to-day. Where 

 I have collected 0. cooperi in the mountain states it is a shell of 

 the " aspen zone." 



Oreohelix is rarely if ever found in abundance except where the 

 country rock is limestone. Some species, in areas largely blanketed 

 by later igneous rock, seem to be wholly restricted to the limestone 

 outcrops. They live on the surface, in dry weather finding refuge 

 under superficial stones, leaves or sticks. Except 0. barbdta in the 

 Chiricahua mountains, I do not remember ever finding Oreohelix 

 below the surface layer of stones or rocks. 



Reproductive Organs of Oreohelix. 



The genitalia have a general resemblance to the same organs in 

 Ashmunella and Sonorella, but there are some differences. There is 

 never a flagellum, though the epiphallus is well developed. The 

 penis-papilla is obsolete or wanting. The penis consists of a lower 

 segment which is longitudinally ribbed within, and an upper segment 

 with thinner walls which are densely papillose within, and enclose a 

 larger cavity. The internally ribbed part is very short in Radio- 

 centrum, but from about a third to over half the total length in 

 Oreohelix proper. The distal end is truncate or quite shortly 

 bicornute. 



In the figures, the organs are shown in nearly their natural positions, 

 except that in some cases the folds of the penis are slightly opened 

 out, to bring the epiphallus into full view. The specific characters 

 are largely a matter of measurements of the epiphallus and penis 

 and its parts. These measurements are taken with dividers after 

 pulling the organs straight, but without stretching. Thus PI. 20, 

 fig. la, and PI. 22, fig. la show the penes of two species pinned out 

 for measuring, after drawing figures in the natural positions. 



