84 HISTORY OF BRITISH CRUSTACEA. 



numbers compensate for its small size. The Rev. Alfred 

 Xorman remarked, that the southern specimens are smaller 

 and paler in colour than those he took in the Clyde, under 

 stones at extreme low water. Mr. Couch* has described a 

 minute Porcellana found by him in Cornwall on a coralline 

 from deep water; he has named it P. acanthoclieles. He 

 says that " on the ridge of the second section of the hand- 

 legs there are two well-marked spines. The carapace in 

 front is divided into three scarcely separated portions." 

 This seems to be only a young specimen of P. longicornis. 



Suborder III. Macroura, Latr. 



This suborder, of which the Lobster is a well-marked ex- 

 ample, is distinguished by the great development of the 

 abdomen, which is generally extended and longer than the 

 carapace ; the seven rings of which it is composed are all 

 movable, and the first five have generally each a pair of 

 false feet, with two terminal plates finely ciliated on the 

 edges, and which act as oars when they swim. The abdo- 

 men is furnished at the end with a large swimming tail 

 formed of five plates arranged like a fan. 



* Cornish Fauna, p. 70. 



