Niphargus Kocliianus and N. subterraneus. 279 



rock, and the granitic chain of the Partly Mountains rises 

 from it steeply into heather-clad summits, the last and most 

 northerly of which is drained on its further side by streams 

 which, wandering down into the limestone lowland, sink into 

 the rock and pursue an unseen course for long distances, till, 

 rising again, they fall into the lake. The number of these 

 subterranean sources at the northern end I am not able to 

 state with certainty, but their volume is considerable. On 

 the S.E. shore, about half a mile from the lake, I visited a 

 natural cavern through which a stream passes, but from 

 whence or whither no one can say. Further to the south, in 

 a bay not far from Lough Mask Castle, the waters of the 

 lake flow with a strong current against the base of a terraced 

 ridge of limestone, which rises in gradual escarpments from 

 the verge, and tlie roar of the disappearing currents can be 

 distinctly heard among the fissured crags. These effluent 

 waters doubtless find their way into Lough Corrib, which is 

 only separated by a low isthmus, about two miles broad, of 

 limestone, through and under which channels exist which 

 void their waters in several magnificent fountains under a 

 cliff near Cong. I look forward to some future opportunity 

 of investigating these interesting districts and the subterranean 

 fauna which they doubtless contain. 



With regard to the Nipliargus, which was finally deter- 

 mined by Dr. Norman to be Kochianus, Bate, very little lias 

 hitherto been published respecting its sexual characters. 

 Spence Bate, who first described the species *, had but a 

 single specimen, which had lost the terminal uropoda. He 

 states that the posterior pair of pleopoda were missing, but, 

 to judge from the figure, all three seem to have been mutilated. 

 Chilton also, in his description of this species, states that for 

 want of a sufficient series for comparison he was unable to 

 put forward any statement of sexual characters. The long 

 series now available from Lough Mask somewhat explains 

 the difficulty, as they show tliat the notable difference in 

 shape and size which characterizes the uropoda of the two 

 sexes in other species of Niphargus does not exist in 

 N. Kochianus. and that therefore they are of little use in the 

 determination of sex. In fresh specimens, however, those of 

 the female seem somewhat more robust and are slightly shorter 

 than those of the male ; but the average difference in length is 

 too inappreciable for the purpose of identification, by itself, of 

 individuals. Moreover, the proportion of their length to the 

 body seems to vary among examples of the same sex. This 



* Nat. Hist. Review, 18o9, yol. vi. rroc Soe. p. 1G5, 



19* 



