BELONGING TO DAPHNIA AND OTHER ALLIED GENERA. 



233 



In Loch Leven, Kinross, this species is found abundantly, and 

 from that locality specimens have been kindly sent to me by the 

 Rev. Dr. I^orman and by Mr. T. Scott. From Loch Lomond 

 also I have recently received specimens taken by Mr. Scott, and 

 I think that others, taken also by Mr. Scott, in the Mill Loch, 

 Mid Yell, Shetland, belong to the same species."^ 



I am indebted to the kindness of Professor Gr. 0. Sars for 

 specimens of D. lacustris from Maridals Yand, near Christiania. 

 These, of course, may be taken as authentic examples of the 

 species which was originally described by that accurate observer ; 

 and one of them is represented in plate X. of the present memoir. 

 In some details it does not seem to agree with Sars' description, 

 notably in the size and shape of the abdominal processes (fig. 20), 

 which are said to be " much shorter than in D. longispma.^'' 

 The Paston Lake specimens — the abdomen of which is figured 

 in plate YIIL, fig. 16 — show processes decidedly shorter than 

 those of D. lacustris, and the Paston species is identified by Prof. 

 Sars as '* one of the numerous varieties of D. longispina , forming a 

 transition to D. hyalina.'''' I believe, however, that D lacustris 

 and D. longispina are really distinct species, and so far as the 

 females are concerned — I have seen no males of D. lacustris, — 

 I should be disposed to lay stress upon the following distinctions, 

 which may perhaps best be contrasted in tabular form : — 



D. lacustris. 



D. longispina. 



Head in the yoiuig bearing a vertex- 

 tooth 



Head in the young without a vertex- 

 tooth 



Forehead veiy prominent in the eye- 

 region 



Forehead not conspicuously promi- 

 nent in the eye-region 



Anterior abdominal process very 

 long 



Abdominal processes short and sub- 

 equal 



Shell evenly tapered at the base of 

 the posterior spine 



Base of the posterior spine distinctly 

 bulging ventrally 



[Colour blueish, Sars.] 



[Coloiu- greenish, Sars.] 



* Mr. D. J. Scourfleld, who has given me most valuable help in the study of Clado- 

 cera, finds in Warren Pond, Ohiijgford, a form which is in every respect identica,] 

 with the Norwegian types of D. lacustris. 



