44 HISTORY OF BRITISH CRUSTACEA. 



the sandy beach between Hayle and St. Ives quite strewn 

 with their exuvise, and he was informed by Mr. K. Couch 

 that the Tohjblus is gregarious, swimming in shoals, and 

 thus occasionally occurring in great numbers on the south 

 coast of Cornwall. 



Polybius Henslowii. Hensloiv s Sivimming Crab. (Plate 

 III. fig. 2.) — Carapace quite smooth and flat above. Body 

 very depressed ; front with five triangular teeth. 



First obtained by Professor Henslow on the north coast 

 of Devon, and subsequently found in various parts of the 

 southern coast of England. It was named by Dr. Leach 

 after the learned naturalist who first discovered it. 



This is named Nipper Crab by the Cornish fishermen. 

 Mr. J. Couch, in his ' Cornish Fauna/* observes that this is 

 more a swimming crab than any of the others ; ' c for whilst 

 the other British species of this family are only able to shoot 

 themselves along from one low promontory to another, the 

 Nipper Crab mounts to the surface over the deepest water 

 in pursuit of its prey, among which are numbered the most 

 active fishes, as the mackerel and Eauning pollack {Merlan- 

 gus carlonarius) , the skin of which it pierces with its sharp 

 pincers, keeping its hold until the terrified victim becomes 

 exhausted. AYe are witnesses of this curious method of 



* Part I. p. 71. 



