ENTOMOSTRACA OF MINNESOTA. 61 



D. palUdus, from whicli ifc differs in possessing a hook on tlie right 

 male antennae. The antennne exceed the caudal setae and are very- 

 slender; that of the male on the right side bears a curved plate or 

 hook which in my specimens is decidedly shorter than the following 

 joint, though said to be equal to it by De Guerne and Eichard. The 

 fifth feet of the female resemble those of palUdus. The inner rami of 

 the male fifth feet are two jointed in the type, but both Marsh and I 

 find forms with one jointed rami. The terminal claw of the right 

 foot is long and geniculately curved, the accessory spine of the pre- 

 ceding segment is near the distal one-third, the inner ramus is (in our 

 form) quite slender, longer than the basal segment of the outer ramus. 

 The terminal joint of the left foot is rounded and ciliated, as well as 

 furnished with two spines. Length of larger forms 1.4 mm., male 

 considerably less. Our small form is 1.1 mm. long and may prove a 

 subspecies, though agreeing with Marsh's figures. Compare also D. 

 siciloides, the western representative of this small form. 



Diaptomus baccillifer Koelbel. 



Plate X, Fig. 2. 



Wierzejski '82 (D. gracilis var. d and b); Koelbel '85; Wierzejski '87 (D. mon- 



tanus); De Guerne and Richard '89. 

 A small species encountered in high latitudes and altitudes of 

 the old world, Siberia and the Alps being the chief stations, is not 

 well distinguished from its allies. The antennae reach the stylets, and 

 in the male the geniculate antenna has a strong process on the ante- 

 penult joint. The internal rami of the fifth feet are more or less dis- 

 tinctly two-jointed, being very short in the female. The inner ramus 

 of the left foot in the male is fused with the preceding segment, and 

 near its base is a spine. The outer ramus of the same foot is forcipate. 

 Length 1.0 to 1.5 mm. 



* Diaptomus shoslione Forbes. 

 Plate V, Fig. 11. 

 Forbes '93. 

 "A very large and robust species. Thorax broadest in front, 

 across the maxillne, tapering gradually, with little convexity to the 

 posterior third. In the female the angle of the last segment is bifid, 

 both projecting points being minutely spinose at the tip. The first 

 segment of the abdomen is laterally expanded; the expansion of the 

 leftside with a minute spine at the apex behind; that on the right 

 produced at the same jjoiut into a small, rounded tubercle, 0.03 mm. 

 in length, about as broad as long, making this first segment somewhat 

 unsymmetrical." '^Egg mass very large, obovate (narrowest for- 

 ward). Right antenna of male robust, the last two joints without 

 special appendages, antepenultimate with a long inarticulate process 

 at its outer apex, extending beyond the tip of the penultimate and to 



