OF THE ENGLISH LAKE DISTRICT. 435 
The recent discovery o£ another species o£ the genus (L. johanseni. Marsh) 
in a tundra pool in Alaska seems to raise a new problem altogether. But 
Marsh's description is very short, and it is not clear that this new species is 
really distinct Irom L. grimaldii or L. macruvus, the only essential diftercnce 
mentioned being the shortness of the furcal rami. It is important that this 
species should be fully described and its distribution ascertained. 
DlAPTOMUS LATICEPS, SlU'S. 
S}'!!. D. hircus, Brady. 
Brady's species, I). Idrcus, was established in ]89l on specimens taken 
from Goats Water, an elevated tarn on the slopes of Coniston Old Man. 
There can be no doubt that his species is identical with I), laticeps, from 
which it differs in no essential character. 
It is an arctic and alpine species occurring mainly in Scandinavia, but 
recorded from Akmolinsk in Russia, the Julian Alps, Serbia, and 
Herzegovina. It has also been taken in several lakes in Scotland and in 
Ireland. 
The only lake in the Lake District in which the species is found is Hawes 
Water, which is the liighest of all (694 feet), and for that reason may have 
a different temperature. It seemed likely that D. laticeps might be common 
ill the high tarns of the district, but, as I have said in my notes on these 
tarns, this is not the case. On the other hand, our knowledge of the fauna of 
these turns is very incomplete, and it may prove to occur in the tarns of 
Harter Fell and to have reached Hawes Water from thence. 
Cyclops abyssokum, Sars. 
This species has been found in all the lakes examined with the exception 
of Ennerdale, Derwentwater, Bassenthwaite, and Esthwaite. In Ennerdale 
no limnetic species of Cyclops was seen in any of the samples taken either 
by Dr. Pearsall or myself, but Brady has recorded the occurrence there of 
C. vicinus. The occurrence of that species in the plankton of this district 
seems most unlikely, and it is more probable that Brady had specimens of 
C. ahyssorum, in which case the species once inhabited Ennerdale but has 
now disappeared. 
Prof. Brady has recorded the occurrence of this species in Windermere 
and Coniston in deep water in Aug. 1883, and Prof. Sars, in his ' Crustacea 
of Norway,' describes it as inhabiting only the deeper layers of water. My 
own collections in Wastwater and Coniston show that, though it is found in 
autumn on the surface, it is distinctly more abundant in deeper water, and 
its absence from Derwentwater, Bassenthwaite, and Esthwaite is no doubt 
largely due to their small depth. It is replaced in these lakes by C. leuckarti. 
In 1911 a few specimens were taken by me in Bassenthwaite, but it is 
evidently not an established member of the plankton in that lake. 
