256 



CRUSTACEANS. 



YO0NG EDIBLE CRAB. 



characterised by having the carapace much wider than long. As an article of 

 food the male is more esteemed than the female, being larger and having larger 

 claws. The two sexes, as in all crabs, may be distinguished by the size of the 

 tails, this organ in the male being narrower, more pointed, and having fewer and 



smaller appendages than in the 

 female. The family Cancridcu 

 is represented in tropical seas 

 by a large number of species 

 and genera, some of which, such 

 as Actcea, have the carapace 

 covered with granules, and 

 ornamented with a network of 

 deep grooves. 



The members of the family 

 Portunidce may be recognised 

 by a modification of the last 

 pair of legs. In the great 

 majority of crabs these legs are 

 like the rest, ending with a 

 long, slender - pointed foot, which bears evidence to its being an organ for 

 running, climbing, or crawling; but in the Portunidce these legs are much 

 flattened, the last segment in particular being dilated into an oval plate. The 

 creatures are thus equipped with a pair of oars, by means of which they swim 

 Several species of the typical genus Portunus are found in British waters, and 

 many of them are hand- 

 somely coloured, although 

 none are such expert 

 swimmers as the tropical 

 species, especially those 

 inhabiting the gulf-weed 

 of the Atlantic. The 

 peculiar motion of the 

 oar -like feet has given 

 rise to the name of 

 fiddler - crabs, so often 

 applied to the group. 

 The figured species 

 (Thalamita natator) is a 

 native of the tropical 

 seas. The common British 

 shore or green crab (Carcinus Tncenas), which is referred to this family, differs 

 from the rest in having the legs of the last pair adapted for walking, being armed 

 with a claw, and not flattened into a paddle. Connecting the present with the 

 following section, is the family Thelphusidce, which contains a number of genera 

 and species found in fresh- water streams, or on land, and sometimes ascending 

 mountains, in temperate and tropical regions. One of the best known species is 



swimming-crab (nat. size). 



