191().] NATURAL SCIENCES OF PHILADELPHIA. 341 



of them are superfluous, either because they are synonymous with 

 other nanus, or because they denote variations not of racial value. 

 In many cases, further collections are requisite, as the small, assorted 

 series of the earlier collectors give no adequate idea of the association 

 of forms in the colonies. Moreover, the location of colonies has 

 often been carelessly recorded, entailing much strenuous field work 

 on the investigator of to-day, work which could have been saved 

 by carefully noting the locations of type localities. 



Distribution of Oreohelix. 



The genus is almost confined to the western mountain region of 

 the United States, but there is one species in southern Assiniboia 

 and one near the southern boundary of Alberta. Formerly one 

 species extended eastward to eastern Iowa. Southward the genus 

 practically reaches the Mexican boundary, in the Big Hachet moun- 

 tains of Xew Mexico and the Huachucas of Arizona; and it will 

 probably be found below the boundary. An outlying species on 

 Catalina Island, California, is widely remote from its kindred, 

 among alien associates. 



A northern and a southern area of speciation may be dis- 

 tinguished. The southern group occupies the southern half of 

 New Mexico, Arizona south of the Colorado River, and Catalina 

 Island, California. It comprises all of the recent species of the 

 subgenus Radiocentrum, and the species of Oreohelix proper which 

 have swollen penes. Species as follows: 



0. concentrata. (Radiocentrum.) 



0. metcalfei. 0. avalo?iensis. 



0. pilsbryi. 0. chiricahuana. 



0. yavapai. 0. clap pi. 



0. barbata. 0. ferrissi. 



0. socori'oejisis. 0. hachetana. 

 0. cooperi. 



Several of these species have one or more subspecies. 0. cooperi 

 occurs only at considerable elevations, and in forms differing some- 

 what from northern specimens. 0. yavapai has been found also in 

 northwestern Wyoming. It is one of the widely distributed species. 

 The other species are special to the southern area. 



In the Florida and Dragoon mountains a few imperfect and very 

 old specimens have been recorded doubtfully as 0. strigosa; but it 

 seems more likely that they belong to the group with swollen penes, 

 some of which resemble 0. strigosa. 



The northern group occupies Arizona north of the Colorado and 



