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HISTORY OF BRITISH CRUSTACEA. 
Chydorus globosus, Baird. — Shell quite globular, six 
times larger than in C. spluzricus , spotted with black. 
Hab. Ponds in the vicinity of London. 
Gen. 150. CAMPTOCERCUS, Baird* 
Oval; abdomen very long, slender, and very flexible, 
much serrated. Beak blunt, slightly curved downwards. 
Camptocercus macrourus, Muller, sp.— Shell pellucid, 
whitish; abdomen very long and slender. The animal, Dr. 
Baird tells us, can twist its abdomen completely round in a 
circle, and then, unbending it, thrust it far out beyond the 
shell. 
Hab. Highgate ponds, and other places near London. 
Gen. 151. ACROPERUS, Baird. 
Shell rounded behind, somewhat harp-shaped, terminating 
in an obtuse point projecting forwards. Lower antennae long. 
Beak blunt, curved downwards. 
Acroperus harPtE, Baird.— Shell strongly ribbed, some- 
what obliquely, giving the shell some resemblance to a harp. 
* Ka/nTTos , flexible, and icep/cos, a tail. 
