400 REV. A. M. NORMAN AND ME. G. S. BEADY 



larger, and more than half the size of the eye ; the centre of the 

 shell is not dark coloured, and the surface is generally smooth, 

 though sometimes more or less reticulated ; the reticulations when 

 present appear more especially on the infero-anteal portion of the 

 shell. Abdomen broad at the base ; the posterior angle not pro- 

 duced, being well rounded off, and armed with about eight fine 

 teeth, in front of which the margin is rather deeply excavated. 

 Length, -roth of an inch. 



Male smaller and narrower, the rostrum shorter and blunter ; 

 the anterior antennae much wider and flatter, having two tentacu- 

 liform seta? on the middle of the anterior margin, and the terminal 

 setae larger and more numerous ; first feet furnished with a large, 

 hook-formed clasping process, the bend of which forms half an 

 ellipse; abdomen of totally different form from that of the female, 

 very narrow, arch-formed, having a very deep concavity exca- 

 vated, as it were, out of the superior margin. It has been pre- 

 viously described and figured by Zenker and Lilljeborg. 



Abundant everywhere, both in large lakes, and small rain 

 pools which dry up in the summer ; in clear or stagnant water. 

 It appears to be a variable species, varying according to the situa- 

 tion in which it lives. It is found in every part of Europe that 

 has been examined. Possibly more than one species may have 

 been confounded in Great Britain under the name L. sjohc&ricus. 

 Schoedler describes a species under the name Chydorus nitidus, 

 and G. 0. Sars has named others Chydorus piger and latus ; and 

 it is probable that these forms occur in our Islands. 



Genus. EURYCERCUS, Baird. 



Head as in Lynceus, but excessively wide, so that the animal, 

 viewed from above, is seen to be wedge-shaped ; the head exces- 

 sively broad, much wider than the valves, and these last gra- 

 dually approaching nearer to each other towards the posterior 

 extremity. Eye-spot small, placed near the eye. Posterior 

 antennae having one branch terminating in three setae and a 

 spine, and another spine at the end of the first joint, the other 

 bearing five setae, and a spine at the extremity. Six pairs of 



