78 UNIVERSITY OF COLORADO STUDIES ' ! 



soil, with the Hayden Survey, Yarrow with the Wheeler Survey and 

 Cockerell working independently were among the early collectors, the 

 latter still continuing his interest, in connection with other branches of 

 natural history. 



In view of the abundance of Mollusca in almost every pond, lake, 

 stream, and water-hole of the plains, to find so few published records from 

 the eastern half of the state and that some of our most abimdant and two 

 of our largest shells are wholly unrecorded was somewhat surprising. It 

 is worthy of especial note that in the plains area almost our only records 

 of fresh-water species, except the few from Lodge Pole Creek and Ft. 

 Morgan, are confined to the area west of a line drawn from Pueblo to 

 Crow Creek, while about the only land snails reported from east of that 

 line are the Succinea collected at Mono, on the eastern boundary of the 

 state. The reason is that local naturalists are not generally interested 

 in conchology and visiting conchologists are usually in haste to reach 

 the mountains. 



There is perhaps no part of the state in which a careful search would 

 not reveal both land and fresh-water shells containing the living animals. 

 This paper does not deal with fossil forms except incidentally. The 

 land snails are with a few exceptions quite small, the principal exception 

 being the genus Oreohelix. This may account for the fact that they are 

 not well known to teachers of zoology or to the general public. The fresh- 

 water snails average much larger, the LimncBas of some species reaching 

 a length of an inch and a half, while several bivalve species reach a length 

 of over three inches. Both land and fresh- water shells are found from 

 the valleys nearly to the top of the range. Almost every pond, lake, or 

 stream will yield some of the latter, while the former may be expected 

 anywhere in damp places under rocks, boards, dead leaves, etc. Gen- 

 erally speaking, they are not apt to be found under resinous trees or 

 among pine needles, but they may sometimes be found even among the 

 pines, in places where there are also quaking aspens and other desiduous 

 trees.' 



Colorado, because of its great variation in altitude, temperature, 

 humidity, and other conditions, and because of the mountains and other 



' Compare V. Sterki, " Shells in Pine Forests," The Nautilus, Vol. V 1891-92, p. n8. 



