gg PROCEEDINOFi OF THE NATIONAL MUSEUM. vol.49. 



decided concavity. At the posterior distal margin of this portion is 

 a short fingerhke process which is not hooked over the other ap- 

 pendage as in S. sealii Ryder. The rest of the appendage is a slen- 

 der structure with an elbowlike bend at about its proximal third, 

 beyond which it tapers uniformly and curves slightly forward. The 

 distal appendage of the third joint is about two-thirds as long as the 

 proximal. Just a little short of the middle it curves rather sharply 

 forward thi-ough nearly 90°. The portion proximal to this bend bears 

 on its anterior margin two fingerhke processes, the distal of which is 

 about twice as long as the proximal. Beyond the bend, this appendage 

 is slightly curved backward and tapers to a point. (Fig. 1.) The 



Fig. 1— Streptocephalus coloradensis. Fig. 2.— Streptocephalus coloradensis. 

 Head op male. X 8. Head of female. X 8. 



coiled vas deferens appears externally on the side of the 13th segment. 

 The two penes are nearly in contact at their extremities and reach 

 not quite to the middle of the 15th segment. 



Average length 22 mm. 



Female. — The first antennae are as in the male. The second 

 antennae are of the usual broad and flattened type and are about as 

 long as the first. The end is rounded, but bears a small spinehke 

 outgrowth at the inner distal margin. (Fig. 2. ) The ovisac is about 

 half the diameter of the abdomen, arises from the 14th postcephalic 

 segment, and reaches about to the middle of the 18th. The eggs are 

 of moderate size and are arranged in four definite rows. 



Average length 23 mm. 



In both sexes there are 1 1 pairs of swimming feet. 



This species is common in two ponds near Eldora, Colorado, in the 

 Front Range of the Rocky Mountains at an elevation of 8,500 feet. 

 I collected material here during the summers of 1913 and 1914. A 

 collection recently sent me from Fort Collins, Colorado, near the 



