ENTOMOSTRACA OF MINNESOTA. | 147 
sexual openings just behind the last pair of feet. It is the upper or 
longer branch of the antenne which in Sida is three-jointed, while the 
reverse is the case in the next genus. The only species, according to 
P. E. Mueller, is the ubiquitous 
* Sida crystallina. 
PLATES XXXYV, Fiaes. 13-15; XX XVII, Fies. 1, 2. 
P. E. Mueller (Daphne crystallina); Latreille (Daphnia crystallina); Straus; Milne- 
Edwards 734-40; Gmelin, Manuel, Fabricius (Monoculus crystallinus); De Geer 
1778 (Monoculus elongatus); Lievin 748; Baird ’50; Lilljeborg ’53; Fischer; 
Schoedler’58 and ’63; Leydig ’60; Sars ’65 (elongata, and crystallina; P. E. Mueller 
68; Kurz ’74; Birge ’78; Herrick ’79, ’82 and ’84; Lutz ’79; Weismann; 
Grobben 779. 
The S. elongata of Sars is distinguished by the smaller head and its 
concave lower margin and more elongate shell. The terminal joint of 
the longer ramus has one less seta than S. crystallina, while the post- 
abdomen has more numerous spines. We incline to believe it a valid 
variety at least. 
GENUS PSEUDO-SIDA Herrick. 
Similar to Sida. Antennules of the female with a long flagellum, 
like that of the male of Sida, sensory setz lateral. Body elongate, 
head short, extending inte a sharp beak. The post-abdomen is armed 
with groups of sharp spines or bristles. Most characteristic, how- 
ever, is the fact that the antennary joint, which in Sida is two-jointed, 
in this species is tri-articulate, and the two-jointed ramus has a great 
number of sete (16 to 17). 
*Pseudo-sida tridenta Herrick. 
PLATES XXXVI, Fias. 2-6; L, Fia. 9. 
Herrick 84 (bidentata. By oversight the number of caudal teeth was misstated and 
the name made to correspond.) and ’87. 
Head very short, acute below, the beak bearing in the female a 
pair of rather large antennules which are armed with a pectinate pro- 
cess three times the length of the antennule, and a cluster of about 
five sensory sete. The antennz are as long as in Sida and well armed. 
The basal joint of the two-jointed branch bears seven sete, the second 
ten setze of which two are apical; three-jointed ramus with very short 
basal segment, second four times as long as wide and armed at the end 
with two setze and a spine; third segment very small, with three setz 
and a minute spine. The maxilla is two-jointed, the terminal joint 
bearing nine jointed spines or short sete. The first foot of the adult 
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