280 
HISTORY OF BRITISH CRUSTACEA. 
cated, or cut sharp and straight. First pair of feet very large. 
Beak sharp, curved downwards. 
Pleuroxus trigonellus, Muller, sp.— Shell somewhat 
triangular, transparent. 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, Muller, sp.— Shell nearly oval, 
and longitudinally striated. 
Hab. Ponds and ditches. 
