76 GEOL, AND NAT. HIST. SURVEY OF MINNESOTA. 



the first joint of the outer branch, and bearing three minute apical 

 set8B. Last joint of the outer branch small, the larger apical seta 

 not reaching as far as the extremity of the claw of the penultimate 

 joint. Inner branch of the right foot in the male simple, mucronate 

 at the apex, and reaching beyond the middle of the last joint of the 

 outer branch; terminal claw of the outer branch strongly falcate, and 

 delicately ciliated on the inner edge; lateral spine attached near the 

 middle of the last joint, long, slender, and finely ciliated. Fifth foot 

 of the left side (male) terminating in a subcrescenti form hyaline 

 lamina, the inner edge of which is delicately crenulated. Length of 

 male and female about 1.55 mm. 



Diaptonms lilljeborgi De Guerne and Richard. 



Plate IX, Fig. 6. 



De Guerne and Richard '88^ and '89. 



This rather large species (2.0 mm. long) is sufficiently identified by 



the greatly expanded inner ramus of the right foot. The last thoracic 



segment is alate and mucronate; the first abdominal being also spined. 



The antennae are scarcely longer than the thorax, and that of the male 



as in D. castor. Algiers. 



Diaptouius roubaui Richard. 

 Plates VIII, Fig. 2; IX, Fig. 11. 

 Richard '88; De Guerne and Richard '89. 

 This, which is perhaps the largest species of the genus (5.0 to 6.0 

 mm.) is recognized by the exi^ansion of the right side of the first ab- 

 dominal segment to form a rounded spinous protuberance while the 

 third and fourth segments of the male are produced and opposable. 

 The antennie scarcely exceed the thorax. The female fifth feet are 

 like those of D. castor. The inner rami of the male feet are one- 

 jointed; that of the right foot being curved and thickened at the apex, 

 that of the left foot indistinctly two-jointed and as long as the basal 

 segment of the outer ramus, which is narrow and armed with spines 

 internally. The terminal joint of the outer ramus is swollen and 

 pilose and armed with two thick spines. 



* Diaptomiis tyrrelli Poppe. 



Plate X, Fig. 9. 



Poppe '88. 



A species from Summit lake (altitude 5, 300 feet, in the Eocky 



mountains) and Centreville, Cal., of moderate size (1.9 mm.) and 



greatly expanded and spined thoracic angles. The first abdominal 



segment is as long as the remainder and expanded and spined ante- 



