STATE GEOLOGIST. 139 



species. The antennae reacli beyond the stylets, the color is dark, 

 the margins of the last segment of the thorax is rather strongly 

 spined, very much as in D. sanguineus. The fifth feet of the female 

 resemble very much those of D. leptopus, but the first segment of 

 the abdomen has a strong spine. The fifth foot of male resembles 

 that of D. sanguineus more than that of leptopus. This species 

 was seen but once, and no measurements can be given save that of 

 the male which was 1.4 mm. 



Sp. 4. Diaptomus armatus, Herrick, 



Is founded upon an imperfectly known form in which the an- 

 tennae do not reach the end of the abdomen; the thickened part of 

 the male antennse short; the antenna armed as in D. sanguineus; 

 the terminal claw of the fifth foot of the male with a tooth near 

 the base; the claw being nearly as long as the ramus. 



Sp. 5. Diaptomus stagnalis, Forbes. 



(Plate Q. Figs. 11 and 13.) 

 D. giganteus, herbigk. 



The largest species of the genus and, not improbably, too close 

 to D. westwoodii, Lubbock. The general characters are like those 

 of D. sanguineus, but the form is much more robust and the anten- 

 nae only moderately exceed the thorax. The proportions may be 

 gathered from the measurements given, In the female the length 

 of thorax is 2.5 mm.; abdomen 1.2 mm.; antennae 2.3 mm.; stylets 

 0.1 mm. The caudal stylets are as broad as long, or nearly so. The 

 last thoracic segment extends into an irregular process 0.1 mm. 

 long, bearing a spine dorsally. The first abdominal segment is 

 spurred on either side. The fifth feet in the female have two-jointed 

 inner rami. The terminal segment of the outer ramus is more than 

 ordinarily distinct, while the claw is biserrate. The right foot of 

 the fifth pair in the male is very long, its claw being strongly tooth- 

 ed. On the inside of the second joint from the base is a disc-like ap- 

 pendage peculiar to this species. The left foot is short. The longer 

 ramus is three-jointed, but the terminal joint is a mere curved spine, 

 opposing a spine from the penultimate segment, which is covered 

 with minute spines or teeth. The basal joint of the ramus has a brist- 

 ly protuberance distally. The inner ramus is marked with oblique 

 ridges. The right antenna has a powerful hooked spine on the 

 antepenult segment, the two segments beyond which coalesce in 



