ACROPERUS. 
129 
short, from last ; posterior branch has only three long 
filaments and one short, from the last joint. 
Abdomen (t. XYI, f. 9 a) very long and slender, with 
thirteen well-marked serrae, or teeth, on lower edge, and 
several smaller ones, terminating in two long and slender 
claws ; setae short. This organ, and lower part of body, 
is extremely flexible, and the animal can twist it com- 
pletely round in a circle, and then unbending it, thrust 
it far out beyond the shell. 
First pair of feet large. 
Intestine convoluted, having one complete convolution, 
and half another. 
Hob . — Ditch near Richmond. Pond near Smallborough 
Green. Hounslow. Hie-hgate ponds. June, July, and 
Genus 4— Acroperus.* 
Lynceus, Baird , Trans. Berw. Nat. Club, i. 
Acroperus, Baird, Ann. and Mag. Nat. Hist., ii ; Trans. Berw. Nat. 
Club, ii. 
Character . — Shell somewhat harp-shaped, terminating 
inferiorly on anterior margin, in a more or less blunt 
point, projecting forwards. Inferior antennae, or rami, 
long. Beak blunt, curved downwards. 
1. Acroperus harpj3. Tab. XVI, fig. 5. 
Lynceus harp^e, Baird, Trans. Berw. Nat. Club, i, 100, t. 2, f. 17, 1835 . 
Acroperus harp^e, Baird, Ann. and Mag. Nat. Hist., ii, 91, t. 3, f. 7, 
1843 ; Trans. Berw. Nat. Club, ii, 151. 
Lynceus leucocephalus,Zo^, Deutsch. Crust., h.xxxvi, 1. 10,1841. 
Shell rounded posteriorly, sinuated rather deeply, and 
ciliated anteriorly ; terminating in an obtuse point, pro- 
jecting forwards ; strongly striated, or rather ribbed, 
longitudinally and somewhat obliquely, giving the shell, 
* Erora aicpog, pointed ; aud 7repag , extremity. 
9 
