PERACANTHA. 
137 
1. Peracantha truncata. Tab. XVI, fig. 1. 
Lynceus truncatus, Muller , Entomost., 75, t. 11, f. 1-6, 1781. 
— Tatreille , Hist. Crust., 206. 
— Baird , Trans. Berw. Nat. Club, 100. 
— M. Edwards, Hist. Crust., iii, 388. 
— ■ Koch, Deutsch. Crust., h. xxxvi, t. 11. 
Monoculus truncatus, Gmelin, Linn. Syst. Nat., 3008, No. 64. 
— Manuel, Enc. meth.,vii,733,t. 268, f. 30-34. 
— ■ Eabricius, Ent. Syst., 498. 
Peracantha truncata, Baird, Ann. and Mag. Nat. Hist., ii, 94, t. 3, 
f. 15, 1843; Trans. Berw. Nat. Club, ii, 151. 
Shell nearly of an oval form, the lower extremity 
having a curved projection backwards, and provided with 
a number of pretty strong spines, about seventeen in 
number, the last three of which are curved backwards. 
On the upper extremity of anterior margin there are 
about an equal number of spines, the upper ones being 
curved upwards. These are partly concealed by the cilia, 
which densely cover the anterior margin of the shell. 
The shell is striated longitudinally. 
Beak rounded and sharp-pointed, rather long. 
Eye areolar; accompanying black spot of a square 
shape. 
Superior antennae conical-shaped; inferior, or rami 
(f.ltf), short. Anterior branch furnished with five setae; one 
from first, one from second, and three from last articula- 
tion. Posterior branch has three setae, all from last joint. 
Abdomen rather gibbous on lower edge, and on latter 
half has about eight spines, and terminates in two stout 
claws. Eirst pair of feet large. 
Intestine convoluted (f. 1 6), having one round and a 
half. Two ova. 
Hab . — Pond at Osterly Park, ditch near Richmond, 
pond at Southall, Middlesex ; summer months. Pool on 
Bowmont Water, Yetholm, Roxburghshire. _> 
