NO. 2226. DISTRIBUTION OF ENT0M0STRACA—D0DD8. 81 



of the alpine lakes are constantly being carried into these lakes by 

 the streams, yet they do not find a footing here, DapTinia pulex 

 bemg found in small numbers in three of them and Diaptomus 

 shoshone in but one. It is equally conspicuous that not only the 

 definitive species, but also other important and common forms of the 

 montane morainal lakes are either wantmg or very scarce here, 

 Diaptomus leptopus being wantmg and Diaptomus longispina, though 

 found in 8 of the 14, was never abundant. On the positive side we 

 may say that the fauna of these lakes comprises 18 species, usually 

 present in very small numbers, most of which are euthermic forms, 

 found at all altitudes. The only species which attains anythmg like 

 abundance is Cyclops hicuspidatus , found in 10 of the 14 lakes, in 5 

 of which it is abundant. Not only does it seem more at home here 

 than does any other species, but it is more abundant here than in 

 any other type of lake studied. The reasons for assigning these lakes 

 to the montane zone are unwillmgness, on the basis of the present 

 data, to constitute them a separate zone; evident separateness from 

 the alpine lakes; their geographical relations; and the fact that most 

 of their species are also found in the morainal lakes of the montane 

 zone. 



These two kinds of lakes I have taken as constituting the montane 

 zone, and because those of the morainal sort are more abundant I 

 have come to think of them as the representative type of the zone, 

 to which I have referred the others. If the latter kind were the 

 more abundant the faunal characters of the zone would be defined 

 quite othei'wise than they have been; but in either case, the dis- 

 tinctness from those above and from those on the plains would 

 remain, and the differences seem in either instance to be due to 

 altitude rather than to peculiarities which might equally well be 

 dupHcated at any elevation. 



As already pointed out, the absence of lakes in the lower portion 

 of the mountain region, a strip about 12 miles wide, makes it impos- 

 sible to get data to show the nature of the fauna in the foothill 

 region and the transition between montane and plains faimas. The 

 small evidence we have bearing on this question seems to indi- 

 cate that probably the chief species of the montane zone continue 

 to be the dominant forms through the foothill area, wherever there 

 are bodies of water. The finding of Diaptomus leptopus, var. pis- 

 cinae (1), D. nudus (2), and DapTinia longispina (1), montane forms, 

 in lakes near Boulder, just at the edge of the plains, though not in 

 plains collections more remote from the mountains, seems to indicate 

 that these species, in the foothill region as in the higher lakes, may 

 continue to be important forms. 



Plains zone. — My own data concernmg the plains lakes are some- 

 what meager, due to the loss, before I had studied them, of a con- 

 3343— 19— Proc.N.M. vol.54 7 ^ ' " 



