BRITISH FRESH-WATER ENTOMOSTRACA. 445 



P. aduncus (Jurine). 



I believe this has hitherto been inckided under P. trigonellus by 

 most writers on British Entomostraca, but it is a good species, 

 and probably not uncommon. 



Chydorus Leach. 

 C. globosus Baird. 



Lynceus globosus Norman k Brady (17). 

 A rather rare species, but widely distributed, 



C. ovalis Kurz. 



C. latus Scourfield (28, 29), Scott (20). 



C. latus Sars. 



Mr. T. Scott has recorded some forms of Chydorus which he 

 thinks belong to this species rather than to C. ovalis, and Mr. 

 Kane has also found it in Lisdoonvarna Lake, co. Clare. 



C. sphaericus (0. F. Miiller). 



Lynceus sphaericus Norman & Brady (17). 

 The commonest and most widely distributed of all the Cladocera. 

 There are several varieties, but none of much importance except, 

 perhaps, coelatus [ = C'. sphaericus yar. favosa Brady (4)|. 



C. barbatus (Brady). 



Lynceus barbatus Brady (4). 

 I cannot make this agree with any of the species recorded by 

 Lilljeborg, although it is evidently close to C. piger. Its chief 

 characteristics are : Ventral shell-margin densely fringed with 

 long plumose setae, posterior margin well rounded but extremely 

 short ; shell-sculpture consisting of ill-defined hexagons giving 

 rise to the appearance of stripes, or rows of dots ; antennules 

 with two olfactory setae at some distance from the other seven ; 

 antennae with only seven swimming setae ; post-abdomen with 

 9-10 long straight teeth followed by a line of fine hairs along the 

 whole length of the anus. Length about ^^ij inch. (See Figs. 11 

 and 12.) 



