96 



GIDEON S. DODDS. 



TABLE I. Concluded. 



counts of localities where each species has been collected. Many 

 of the records are indefinite or very general and do not enable 

 one to judge just what zone is included. The tabulation, in spite 

 of this, contains much of truth and I have attempted to confine 

 its errors to those of omission. The Tropical Zone has been 

 omitted, chiefly because I have been unable to determine cer- 

 tainly which species in my list extend into it. It is likewise diffi- 

 cult to determine which species range into the Arctic-Alpine. 



The agreement between the local and general zonal range is 

 striking, and in many cases, complete. The only departures from 

 this agreement are in the cases of certain species for which the 

 local records do not cover as many zones as the general. These 

 species are mostly those which are not abundant and have been 

 met with infrequently in the Colorado collections, such as certain 

 species which are never present in more than very small num- 

 bers and may easily be missed in making collections, or others, 

 which though found occasionally in abundance, are met with in 

 only a small proportion of the lakes in the zones which they in- 

 habit. More extensive collections would doubtless extend the 

 records of many of these species to cover other zones and so 

 bring the local records into still closer agreement with the general. 



