THE MOLLUSCA OF COLORADO 



l8l 



Voight at Canyon City, and two found by Mr. A. Dakan in a spring near Boulder Falls, 

 in the mountains west of Boulder. In view of the abundance of the species at Boulder 

 and its wide distribution it is surprising to find a dearth of records for the state. 



Genus PLANORBIS Guettard 



Planorbis trivolvis Say. Fig. 40 



Saguache, Yarrow 68, 946. 



Hdisoma trivolvis. Between Animas and LaPlata and at 

 San Luis Lakes. Ingersoll 35, 404. 



One of the most abundant mollusks in lakes, ponds and 

 some small, sluggish streams from Boulder northward to Crow 

 Creek, dead shells sometimes thickly covering the beaches of 

 old irrigation reservoirs, usually associated with Physa sp. and 

 Planorbis parvus. We also found great numbers in a mountain 

 lake in Estes Park. Specimens received from Prof. E. A. 

 Kenyon were collected at Florence, and some from Prof. Cock- 

 erell were collected at Lake George. 



Fig. 40. — Planorbis tri 

 vol vis. 



Planorbis trivolis plexata Ing. 



St. Mary's Lake, type locality, Ingersoll 35, 389, 402. 



Planorbis bicarinatus Say. Fig. 41. 



Lodge Pole Creek, collected by Mr. C. T. Simpson, Cockerell 

 22, 61. 



We have found a few in Owen's Lake, in a sluggish stream east 

 of Boulder and in northern Weld County, and noted a few in the 

 collections of the State Normal School at Greeley. 



Fig. 41. — Plan- 

 orbis bicarinatus. 



C^J) 



Planorbis parvus Say. Fig. 42. 



South Park, Yarrow 68, 947. Subfossil at Grape Creek, Cock- 

 erell Mss. Empire (Pilsbry), Buzzard Creek (Cockerell), North Park 

 (E. A. Barber), South Park (Smithsonian), Trinidad (Pilsbry), Vanatta 

 Mss. 



Gyraulus parvus. Hot Sulphur Springs, Arkansas River, 10 miles 

 below Granite, between Rio Animas and LaPlata, St. Mary's Lake and 

 North Park, Ingersoll 35, 404. Davidson's Ranch, Ingersoll 37, 133. 

 Abundant on vegetation, rocks, sticks, etc., from Boulder to Crow 

 Creek, extending into the mountains up to at least 9,000 feet. Specimens received from 

 Prof. E. A. Kenyon were collected at Florence. We have received two specimens from 

 Prof. E. Bethel, found fossil by Prof. Geo. L. Cannon in ancient overwash of the South 

 Platte River near Denver. 



Fig. 42. — Plan- 

 orbis parvus. 



Planorbis umbilicatellus Ckll. 



Davidson's ranch, Vanatta 65, 117. 



A day spent in searching for this species at Davidson's ranch resulted in great 

 numbers of parvus, hut not a single umbilicatellus. As it is not a case of mistaken iden- 

 tity, has the species disappeared from there ? 



