80 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 54. 



of the several species, as for instance, the less restricted nature of 

 Daphnia pulex and Biaptomus coloradensis, evidenced by their more 

 uniform correlation percentages, contrasted with the wide variability 

 of correlation of each of the other three species. In using such figures 

 care must be exercised not to attach to them greater significance 

 than is justified on the basis of the number of localities collected and 

 the frequency of occurrence of the various forms, but in this table 

 I suspect that the significance of the figures is less, rather than 

 greater, than the actual facts, because, in some cases, two species 

 are computed as living in the same lake when one of them is plainly 

 the dominant form and clearly belongs there, while the other one is 

 present in small numbers and barely manages to exist. 



In a similar manner I computed correlation percentages between 

 all the species in my collections, and though such figures when ar- 

 ranged in the form of a table were useful in the analysis of my data 

 they do not seem of sufficient importance to publish. I merely sug- 

 gest this as a possible means of analj^sis for other data of this sort. 



The following northern species, which range southward along the 

 mountain range, are entirely or nearly confined to these lakes, and 

 belong primarily to the montane zone: Lim.netis gouldii (3 lakes), 

 Latona setijera (1), Holopedium gihherum (9), Eurycerus lamellatus 

 (8), Acroperus harpae (11), Camptocercus rectirostris (2), Alonella 

 excisa (2), and Alonella exigua (1). Two other species worthy of 

 mention are Diaptomus lintoni (2), described from the Yellowstone 

 region, and Diaptomus nudus (5), described from lakes at Pikes Peak 

 at 11,000 feet, apparently under alpine conditions, but in the Tolland 

 region not found above the montane zone. Simoceplialus vetulus 

 (22), the dominant Cladoceran in marshes and weedy pools of this 

 zone, is widespread and common in all zones except the alpine, from 

 which it may be shut out by the lack of plant growth rather than 

 by extreme climatic conditions, an indirect rather than a direct effect 

 of altitude. Chydorus spliaericus and four species of Cyclops are 

 common here but have no significance as they are met with every- 

 where. Other species not of special significance may be learned by 

 reference to Table 4. 



Of the other lakes of this /one, the 14 on stream courses, it is 

 difficult to give a good characterization. At first I was inclined to 

 place them in a separate zone, the subalpine, but because of the lack 

 of lakes of this type in elevations below 10,000 feet it is not possible 

 to tell which of their faunal characters are due to altitude. Barker 

 Reservoir (8,200 feet), a lake of the same sort, has somewhat similar 

 faunal characters, a fact which leads me to suppose that their fauna 

 does not give place to a different one in lower altitudes. 



That these lakes are definitely distinct from those of the alpine 

 zone is clearly indicated by the fact that while the dominant foi-ms 



