THE NAUTILUS. 117 



which have been identified by Mr. Bryant Walker as Anodonta 

 danieki Lea. This collection constitutes the first record of this 

 species from Colorado. The only other species of Anodonta 

 known to occur in Colorado is Anodonta grand-is, listed from two 

 localities, Lodgepole Creek in the extreme northeastern corner 

 of the state and a reservoir about 30 miles north of Denver. 

 (Henderson, Mollusca Colo. 1912). 



The stream, Black Wolf Creek, is a small, rapid, spring-fed 

 brook, about seven miles long and averaging two feet wide dur- 

 ing low water. It joins the Arikaree River about eight miles 

 from the Colorado-Nebraska line. As the Arikaree River fre- 

 quently goes dry in Colorado during the summer months, Black 

 Wolf Creek which carries water throughout the year from its 

 small springs, is left an isolated unit during these dry seasons. 

 The bottom of this stream is coarse sand or fine gravel except 

 in the backwaters upstream from the two artificial dams which 

 have been placed across the stream to deflect water for irrigation 

 purposes. Back of each of these dams the stream widens to 20 

 feet or more for a distance of several hundred yards, in which 

 portions of the stream the water averages four feet in depth. 

 In this quiet water the fine blue clay carried by the stream has 

 been deposited on the bottom in a compact layer about 20 

 inches thick. 



The colony Anodonta danielsi was found in the deep water 

 back of the upper dam on Black Wolf Creek, which is located 

 about two and one- half miles north and a little west of the 

 Indian battleground known as Beecher's Island. This dam is 

 little more than a low mud wall and it has not increased mate- 

 rially the depth of the water in a naturally deeper portion of the 

 stream. This fact together with the finding of large numbers of 

 broken shells on and in the banks of the stream where they had 

 been carried by mammals, and the absence of shells in the deep 

 water back of the lower dam (a more elaborate wall which has 

 changed the water-level back of it) suggests that the colony 

 found has been established for a long time. The individuals 

 were very abundant, often six or more large adults occurring in 

 a space a foot square. Each shell was securely buried in the 

 dense blue clay so that a rather strong pull was required to 



