N 



CRUSTACEANS ,-j 



legs, which are used mainly for cleansing the other appen- 

 dages. Like most crustacea they are scavengers and 

 bellicose to a degree. 



The Brachyura or Short-tailed Crustacea comprise a 

 vast legion known as the true crabs, and are built upon 

 the same lines as the Long-tailed Crustacea, both externally 

 and internally. Like the lobsters and hermit crabs they 

 have a large membraneous stomach, and like the lobsters 

 are virtually omnivorous. The tail, however, is doubled 

 under the body and is broad in the female and narrow in 

 the male. True crabs not only abound between tide marks 

 but have also penetrated to the abyss, some having adapted 

 themselves to an entirely pelagic existence in the surface 

 waters, whilst others have travelled far up the rivers 

 and even invaded the dry land. This great range of 

 environment has inevitably involved great diversity of 

 form and habits, and the group has been altogether more 

 completely studied than many other branches of the 

 crustacea. 



The crabs are divided into five main groups or tribes. 

 The first includes the most primitive members and are 

 known as Sponge Crabs, of which one species is commonly 

 found off our southern coasts, usually in fairly deep water. 

 It is a slow-moving, clumsily-built creature, with its 

 last two pairs of legs so constructed that they serve to 

 hold a sponge or shell over the creature's back like a 

 canopy, and thus hidden from foes it goes its way though 

 considerably hampered. 



A remarkable member of the group has been added to 

 the British fauna only within the last few years. It is 

 a giant amongst crabs, having a leg span of nearly 48 



