ay ap yin SR ne aaa thee See eR Ge 
76 GEOL. AND NAT, HIST. SURVEY OF MINNESOTA. 
the first joint of the outer branch, and bearing three minute apica] 
sete. 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. 
Diaptomus lilljeborgi De Guerne and Richard. 
PLATE IX, Fia. 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 antenne are scarcely longer than the thorax, and that of the male 
as in D. castor. Algiers. 
Diaptomus roubaui Richard. 
PLATES VIII, Fia. 2; IX, Fia. 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 expansion 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 antenne 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. 
* Diaptomus tyrrelli Poppe. 
PLATE X, Fie. 9: 
Poppe ’88. 
A species from Summit lake (altitude 5,300 feet, in the Rocky 
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- 
