Notes on the Crustacean Fauna of the English Lakes. 421 



Lynceus macrourus, Mull., is much rarer than the pre- 

 ceding species, to which it bears a striking general resemblance. 

 Buttermere, Der went water, and Blea Tarn (Langdale) are 

 the only localities in the Lake district where I have met with 

 it. It seems to be a lowland rather than an alpine species. 



Lynceus quadranguiaris, Mull., is still more decidedly of 

 lowland proclivities, being quite one of the rarer species in 

 mountainous districts, but almost the commonest of British 

 Lyncei in the plains. I have taken it, however, sparingly in 

 Grasmere, Easdale Tarn, Derwent water, Blea Tarn (Lang- 

 dale), and in pools in Ennerdale. Its place in the waters of 

 the lowlands seems in mountain regions to be usurped by the 

 following species : — 



Lynceus elongatus (G. O. Sars) — Fig. 8 — which may be 

 looked upon as the form most characteristic of mountain lakes, 

 its strongholds being bleak, elevated sheets of water, such as 

 Stickle, Angle, and Sprinkling Tarns, while at low elevations, 

 and especially in small pools, it is much scarcer. In the low- 

 land and southern districts of England it is not at all met 

 with. When living in high, bleak tarns, it is often of a very 

 deep, opaque brown colour, verging on blackness, and some- 

 times appears to be almost the only animal inhabitant of the 

 water ; but in lower and more sheltered situations it to a great 

 extent loses its deep colouring. A very remarkable peculiarity 

 of L. elongatus is that the carapace, though normally consisting- 

 of two valves, like all the rest of the genus, is very often 

 found to be made up of two or three pairs of valves superim- 

 posed one on another. This condition is seen in the specimen 

 represented at Fig. 8 of our plate, the six layers of carapace 

 being plainly indicated by the minute tooth at the lower pos- 

 terior angle of each. In this condition the edges of the several 

 valves occupy very various positions. Sometimes all three 

 (and I have never seen more than three) are pretty close 

 together, as in the figure; at other times the edge of the 

 uppermost comes nearly in the middle of the animal. It is 

 remarkable, too, that the several coats do not separate in the 

 process of exuviation, for the sloughs, which are often taken 

 in great numbers along with the living animals, constantly 

 show the several valves in union just as when alive. I cannot 

 yet say whether the young are born in the multivalvular state, 

 or whether it is a result of growth, but in every copious 

 gathering of L. elongatus many specimens in this condition are 

 sure to occur, and in some they form almost the greater part 

 of the whole. This is the more interesting when considered 

 in relation to a very curious species of the same family, 

 Monosjnlus tenuirostris, one striking character of which con- 

 sists in a somewhat similar but much more pronounced multi- 



