Daphnia longiremis. 299 



a small one may easily be present. Sars now ('90, p. 10, 33.) 

 regards the species as a variety of D. galeata. I do not follow 

 him in this as my material does not warrant the change. In- 

 deed I find it difficult to understand his later classification of 

 the species D. galeata and D. hyalina with their numerous 

 varieties. 



Daphnia longiremis, Sars. 

 Plate XI, Figs. 4, 5, 7, 8, 9, 10, 11, 12. 



There is only one description of European specimens of this 

 species, that of Sars ('62, p. 148.). Schoedler ('66, p. 30.) 

 and Eyimann ('86, p. 42.) both take their descriptions from 

 Sars' original account, as also does Herrick ('84, p. 73.). Sars 

 in his later paper makes this species a variety of D. cristata 

 ('90, p. 10, 35.). 



Sars' account is silent on some points of structure which are 

 quite conspicuous in my specimens, so that I am not sure that 

 they belong to Sars' species, but as they agree in general struc- 

 ture and especially in the great length of the antennae I prefer to 

 keep them here rather then to make a new species on doubtful 

 grounds. 



The specimens examined are pellucid and greatly compressed 

 laterally. The valves as seen from the side are broadly ellip- 

 tical. The spine is long, very slender, and inserted a little 

 above the middle of the valves and is directed somewhat 

 dorsally. It is armed on the side with small spinules. These 

 extend along the ventral margin of the shell but do not go be- 

 yond the base of the spine on the dorsal side. The reticulation 

 of the valves is very indistinct, almost invisible in alcoholic 

 specimens. 



The head is small, evenly rounded in front ; the ventral mar- 

 gin straight, slightly convex or slightly concave. The rostrum 

 varies greatly, being in some examples a long, pointed nose, and 

 in others practically absent. The figures give a good idea of the 

 range of variation. 



The antennae are very long and slender. When reflexed they 

 extend nearly to the base of the spine but never quite reach it. 



