280 HISTORY OF BEITISH CRUSTACEA. 



cated, or cut sharp and straight. First pair of feet very large. 

 Beak sharp, curved downwards. 



Pleuroxus trigonellus, Miiller, sp. — Shell somewhat 

 triangular, trail? parent. Beak curved downwards. 



Hab. Ponds in England and Scotland. 



Pleuroxus uncinatus, Baird. — Shell somewhat trian- 

 gular, fluted. Beak curved upwards. 



Hab. Pond between Hanwell and Southall. 



Pleuroxus hamatus, Baird. — Much smaller than either 

 of the preceding, and very transparent. 



Hab. Yetholm Loch. Dr. Baird says this may prove to 

 be the male of the first species. ■ 



Gen. 154. PERACANTHA, Baird 

 Oval ; lower extremity of the shell somewhat curved back- 

 wards and along with the upper end of the front margin, 

 beset with strong hooked spines. Beak sharp, curved 

 downwards. 



Peracantha truncata, Miiller, sp. — Shell nearly oval, 

 and longitudinally striated. 

 Hab. Ponds and ditches. 



