106 
BRITISH ENTOMOSTRACA. 
to make out this articulated structure distinctly. Like 
the antennules of the Daphniadae 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 Daphniadae. 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. 
Hab . — 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 — Sid a. 
Sid a, Straus, Mem. Mus. Hist. Nat., v; M. Edwards, Baird, Dana. 
Daphnia, Muller, Latreille, Bose , &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. 
