THE MOLLUSCA OF COLORADO 169 



We have received dead specimens collected by Professor F. H. Hopkins at Meeker 

 and by Mr. A. Dakan at Muddy Creek, Bear River above Hayden and above Steamboat 

 Springs, and 15 miles north of Craig, all in the western part of the state, and found one lot 

 of five semi-fossil specimens at Boulder. Some of the foregoing records probably refer 

 to strigosa, but they are here inserted just as they occur in the Hterature. The fact that 

 few live ones have been found appears to indicate that it may be on the rapid road to 

 extermination through a considerable part of its range, a matter well worthy of investi- 

 gation. Professor Cockerell suggests to the writer that its higher spire renders it less 

 fitted than strigosa to survive in a semi-arid country, because of the greater difficulty of 

 getting under rocks, etc., to avoid the dry heat. This, however, would not account for 

 the extinction of haydeni, which is a depressed form. An investigation of species 

 recently extinct or approaching extinction may throw some light upon recent changes in 

 cUmate. 



Oreohelix cooperi trifasciata Ckll. 



Mesa County, Cockerell 12, 8; 14, 102; 23, 175. Gleneyre (S. M. Edwards), 



Vanatta Mss. 



Oreohelix haydeni Gabb. 



Glenwood Springs (Silas L. Schumo), Vanatta Mss. 



We have just received from Professors E. Bethel and G. L. Cannon about 35 speci- 

 mens of this species which call to mind Binney's assertion that it must be considered a 

 variety of strigosa. The series passes from very strongly ribbed specimens by minute 

 gradation to those almost entirely smooth. The color bands, when not obhterated by 

 bleaching, are as in ordinary strigosa. The spire varies from greatly depressed to highly 

 elevated forms, thus connecting strigosa and cooperi. The specimens referred to above 

 were found fossil together at Glenwood Springs by Miss Mabel Steams. This affords 

 food for thought, especially when considered in connection with the facts that haydeni 

 seems nearly extinct, cooperi is apparently extinct through a great portion of its range, 

 and strigosa seems much less common in many places than formerly. It is not at all 

 unhkely that further field-work may bring to light the origin and the beginning of the 

 extinction of these forms. 



Genus THYSANOPHORA Strebel & Pfeiffei 



Thysanophora ingersolli Bland. 



San Juan, Custer and Mesa Counties, Pilsbry and Johnson 43, 15. Near Buzzard 

 Creek, West Fork Clear Water Creek, and Ouray, Cockerell Mss. Clear Water Creek 

 and Custer County (specimens from Cockerell), Vanatta Mss. 



Microphysa ingersolli. Baker's Park, Cunningham Gulch, Animas Valley and 

 North Park, up to 11,000 feet, Ingersoll 35, 389, 398. Saguache Mts., Ingersoll 37, 

 130. Saguache Mts., Las Animas and LaPlata Counties, Howardsville and Cunning- 

 ham Gulch, Binney 6, 170. Western Custer County and Grand Mesa, Cockerell 22, 

 62, 65. 



Pyramidula ingersolli. San Juan, Custer and Mesa Counties, Cockerell 14, 103. 



We have found a few above Eldora, at an altitude of over 9,000 feet, and four small 

 specimens at Boulder. The latter were accidentally destroyed. 



