•- PERACANTHA. 137 



1. Peracantha truncata. Tab. XVI, fig. 1. 



Lynceus tkuncatus, Mailer, Entomost., 75, t. 11, f. 4-6, 1781. 



— Latreille, Hist. Crust., 206. 



— Baird, Trans. Berw. Nat. Club, 100. 



— M. Mwards, Hist. Crust., iii, 388. 



— Koch, Deutsch. Crust., h. xxxvi, t. 11. 

 MoNOCULUS TRUNCATUS, GmeliH, Linu. Syst. Nat., 3008, No. 64. 



— Manuel, Enc. meth.,vii,733,t.268, f. 30-34. 



— Fabricitis, 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.l«), 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. Pirst pair of feet large. 



Intestine convoluted (f. 1 h), 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. 



