20 TWELFTH ANNUAL REPORT. 



flagellum. Second antennae with the rami two and three-jointed. 

 Male with the sexual openings just behind the last pair of feet. 

 It is the upper or longer branch of the antennae which in Sida i& 

 three-jointed, while the reverse is the case in the next genus. 

 The only species, according to P. E. Mueller, is the ubiquitous S. 

 crystallina. 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. The 

 bibliography below is extracted from a previous report: 



DapTine crystallina, Muellek. 



Daphnia crystallina, Latreille, Bosc. 



Sida crystallina, Straus, Mem. Mus. Hist. Nat. 



Sida crystallina, M. Edwards, Hist. Nat. Crust. 



Monoculus crystallinus, Gmelin, Manuel. Fabricius. 



Monoculus elongatus, De Geer, Mem. servir. Hist. Ins. 



Sida crystallina, Lievin, Branch, d, Danziger Geg. 



Baird, Brit. Entom. 



LiLiiJEBOBG, De crust, ex ord. trib. 



Fischer. 



SCHOEDLER, Die Brancb. d. Umg. v. Berlin. 

 Neue. Beitr. 



Leydig, Naturg. d. Dapb. 



Sars, Norges Ferslcv— Krebsdyr. 

 Sida elongata. Sabs, " *' " 



Sida crystallina, P. E. Mueller, Danmarlc's Cladocera. 



KuRZ, Dodekas Neuer Cladoceren. 



Birge, Notes on Cladocera. 



Herrick, Microsc. Entom. 



LUTZ, Untersuch, u. d. Cladoceren d. Umg. v. Bern., 1878. 



Weismann. 



Grobben, Entwicklung. Moina. 



Herrick, Crustacea of Minnesota. 



II. — Genus Pseudo-sida. Herrick. (Genus n.) 



Similar to Sida. Antennules of the female, with a long flagel- 

 lum, like that of the male of Sida, sensory setae lateral. Body 

 elongate, head short, extending into a sharp beak. The post- 

 abdomen is armed with groups of sharp spines or bristles. Most 

 characteristic, however, is the fact that the anteunary joint, which 

 in Sida is two-jointed, in this species is tri-ariiculate, and the two- 

 jointed ramus has a great number of satae (16-17). 



Sp. 1. Pseudo-sida bidentata, Herrick. (Sp. n.) 



(Plate K. Fig. 9.) 

 Post-abdomen armed with 12-14 clusters of spinules in a trans- 

 verse row ; the terminal claw armed with two long basal spines, 

 and with numbers of fine teeth on the inside. The two-jointed 



