106 BRITISH ENTOMOSTRACA. 



to make out this articulated structui'e distinctly. Like 

 the antenuules of the Daphniadse and Lynceidae, they 

 appear to be almost destitute of motion, and thus when 

 seen close to each other, they certainly bear a close re- 

 semblance to a prolongation of the beak. The inferior 

 antennae, though strong bodies, are much shorter than in 

 most of the Daphniadff'. The anterior branch has four 

 articulations ; the posterior only three. They are furnished 

 with long filaments, which are not plumose. The ova are 

 few in number. 



The motion of this curious little creature through the 

 water is caused by numerous and very rapid strokes of 

 its inferior antennae or rami, being in that respect very 

 similar to the Lyncei. The males I have never met 

 with. 



Hah. — New River, London ; Highgate ponds. I have 

 every summer for several years past met with it abundantly 

 in the common drinking-water of London supplied from 

 these two sources. 



SIDINA. 



Genus 1 — Sida. 



SiDA, Straus, Mem. Mus. Hist. Nat., v ; M. Edwards, Baird, Dana. 

 Daphnia, Muller, Latreille, Bosc, &c. 

 MoNOCULUs, Be Geer, Jurine, &c. 



Character. — One branch of inferior antennae with three, 

 the other with two articulations, large and powerful. 

 Superior antennae of moderate size. 



