14 PROCEEDINGS OF THE NATIONAL MUSEUM vol.75 



DIAPTOMUS NOVAMEXICANUS Herrick, 1895 



D. novamiexicanus was described by Herrick from material col- 

 lected at Albuquerque, N. Mex. It has been found in only one other 

 locality — Burbank, Utah. It may be noted that in Herrick's de- 

 scription it was stated that the second segment of the exopodite of 

 the fifth foot of the female bears two spines. In the material ex- 

 amined by the author there has been a third minute spine on this 

 segment in some individuals. The distribution of the species is 

 shown in Figure 5. 



DIAPTOMUS NUDUS Marsh, 1904 



D. rmdiDS was described from collections made by Prof. H. B. Ward 

 in lakes in the vicinity of Pikes Peak, Colo. ; Dead Lake, Lake Michi- 

 gan, Lake Rocks, and Mirror Lake. Dodds, 1908, reported it at 

 Boulder, Colo., and in 1915a: from Tolland, Colo. It has also been 

 found in Colorado, at Kremmling, and in a pond in the city park, 

 Denver. Quite recently it has been collected in Utah Lake, Utah, and 

 in Jacobs Lake in the Kaibab National Forest in Arizona. Its dis- 

 tribution is shown in Figure 5. 



DIAPTOMUS OREGONENSIS Lilljeborg, 1889 



D. oregonensls was first found near Portland, Oreg. It has re- 

 cently been reported by Brehm from Vancouver, British Columbia, 

 It is rather strange that these are the only reports of its occurrence 

 on the Pacific side of the continent. Herrick collected it in Lake 

 Minnetonka, Minn., and it was found in collections made by Doctor 

 Hemingway in Lake Vermilion in northern Minnesota. It occurs 

 m many lakes in Wisconsin and northern Michigan. It is in Lake 

 Superior, Lake Michigan, the Detroit River, and Lake St. Clair and 

 in Lake Erie. Without much doubt it is in Lakes Huron and On- 

 tario, although it has not been reported from them. Stromsten, 1917, 

 found it in the Okoboji Lakes in Iowa. It occurs in northern Illi- 

 nois and Indiana. Pearse's 'p^ygnvoieus^ which is without doubt ore- 

 goiiensis^ was found in eastern Massachusetts. Klugh, 1926, found 

 it in New Brunswick and the Province of Ontario. Doctor Congdon 

 collected it at Kinistino, Saskatchewan, the most northern point of 

 its known range. In the region of the Great Lakes it is the most 

 common species of the genus. Its distribution is shown in Figure 6. 



DIAPTOMUS PALLIDUS Herrick, 1879 



D. palUdus is widely distributed in the general region of the 

 Mississippi Valley. Herrick, in his original description, speaks of 

 it as abounding in the larger lakes of Minnesota and later says that 

 it is in the entire Mississippi Valley. Stromsten, 1917, found it in 

 the Okoboji Lakes and Brewer, 1898, and Pearse, 1905, found it 



