232 ON THE BRITISH SPECIES OF ENTOltOSTEACA 



Generally it seems te have more in common with D. longispina 

 than with D. lacustris. A gathering made by the Rev. Dr. 

 Norman in Mochrum Loch, Wigtonshire, contains specimens of 

 similar character. 



Whilst these pages have been going through the press I have 

 received from Mr. T. Scott a second very interesting gathering 

 from Loch Arklet, containing females of the ordinary kind 

 together with many males and ephippial females. This collec- 

 tion was made late in the season — November. The males are 

 very similar to those from Paston Lake, Northumberland, which 

 I have described and figured as D. longispina. Sars does not 

 appear to have seen the male aquilina. 



Daphnia lacustris, G-. 0. Sars, (PL X., figs. 19, 20). 

 var. vicina, Richard, (PI. YII., figs. 18-21). 

 1862. Daphnia lacustris, Gr. 0. Sars, Om de i Omegnen af 

 Christiania forekommende Cladocerer (andet 

 Bidrag), p. 19 (separate copy). 

 1896. ,, lacustris, var. vicina, Richard, Revision des 



Cladoceres (Annales des Sciences Naturelles), 

 p. 307, pi. XXIY., fig. 1. 

 The typical form of this species (pi. IV., fig. 19) is very simi- 

 lar to D. longispina, but the head is flatter in front and the 

 forehead more prominent in the eye-region, behind which the 

 lower border of the head runs backwards almost in a straight 

 line, and ends in a sharp but not very prominent beak, the 

 hinder margin only slightly sinuated, protuberance of the anten- 

 nule very slight. Spines of the post-abdominal laminae 9-12 in 

 number ; abdominal processes confluent at their bases, the ante- 

 rior process very long, much longer than the terminal unguis. 

 Base of the shell-spine without any anterior bulge. Length, 

 1.55 mm. 



The form described by M. Richard, from Loch Leven speci- 

 mens, as a distinct variety (vicina) is founded chiefly on the 

 presence of a small tooth on the top of the head (pi. YIL, fig. 21). 

 This, however is a character of the young only, disappearing 

 altogether in the adult (fig. 19). 



