Chap, ii.] 



FRESHWATER CRUSTACEA. 



53 



come out in wet weather. I did not see any of them. The 

 boys kept up a constant shouting, which resounded through 

 the valley. 



At the bottom of the valley is a small stream running rapidly 

 over the stones, like a trout stream, and everywhere very shal- 

 low. In this stream grow wacercresses and several familiar 

 English water plants, and I found two ferns on the banks. 

 Two kinds of freshwater shrimps live in the stream under the 

 stones, and are very abundant, notwithstanding the shallowness 

 of the water. One is a Palaemon, a large prawn, as big as the 

 largest specimens of our common river crayfish, and with long 

 and slender biting claws. 



The other kind is a very different animal, somewhat smaller, 

 and of the genus Atya, which is distinguished by having no 



ATYA suLCATiPES. (Natural size.) 



a One of the front pairs of walking legs. Beneath ; the same pair enlarged ; 

 a the nippers widely open ; b the crescent-shaped joint to which they are hinged 



nippers on the larger pairs of walking legs, but only simple, 

 spine-like ends to them. The two front pairs of walking legs 

 have, however, most extraordinarily shaped claws at their extre- 

 mities ; quite unlike any occurring in other Crustacea, except 

 the Atyidse, as will be seen from the figure. These claws or 

 nippers have slender arms of equal length and dimensions, 

 which are linked together so as to open and shut like a pair of 

 forceps, closing flat against one another. 



At their extremities these forceps arms are provided with 

 thickly-set brushes of long hairs, as long as the arms them- 

 selves. These hairs expand in the water when the forceps 

 are opened, and evidently form a widely-sweeping, grasping 



