THE HABITS OF THE LAND CRABS. 389 



of very unequal extent ; the former being by far the 

 most numerous, and the former are likewise subdivided 

 into two further groups according to whether their eyes 

 are pedunculated or sessile. 



(352.) Those with pedunculated eyes are subdivided 

 into decapod andstomapod Crustacea. The former of these 

 contain the greatest number of genera throughout the 

 group, and also considerably the largest animals : they 

 have usually five pairs of legs, and are subdivided into, 

 first, decapod Brachyura, known as crabs. The structure 

 of the abdomen of which is very remarkable, forming a 

 sort of leaf, disproportionately small, and which folds 

 back upon the under side of the thorax. It is quite im- 

 possible that we should go into further detail here of their 

 subdivisions ; and all that we can do, therefore, will be 

 to exhibit some of the more prominent genera, distin- 

 guished either by their economical uses or their habits. 

 Amongst them is the genuine crab of our tables, the 

 Cancer Pagurus, the type of the entire group, the 

 flesh of which is much esteemed and considerably used. 

 Among the quadrilateral crabs, we observe the genus 

 Thelphusa, peculiar for inhabiting fresh waters, and the 

 power they possess of living a week or even a month 

 away from the water. These animals are common in 

 the limpid lakes and streams of the South of Europe, 

 and are sought as great delicacies. It is this species 

 which is represented upon the ancient coins of Agri- 

 gentum in Sicily. In this same division we find the 

 genera Gecarcinus and Cardisoma. These are the ce- 

 lebrated Tourlourous, or land crabs, called also violet 

 crabs and white crabs from their colour, and are natives 

 of the West India islands and South America. They 

 are very courageous, and try to intimidate by the clatter 

 of their claws, and they pinch very severely. The 

 history of these creatures presents some of the most 

 extraordinary phenomena throughout entomology, that 

 we cannot forbear giving a rapid sketch of it. Their 

 usual habitat is in the mountains, away from the sea 

 and water, where they reside within cavities or burrows 

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