LOBSTERS, CRAYFISH ,, ETC. 
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antennae are furnished with a distinct basal scale-like plate. The first family 
(Eryontidce ) contains several genera found in deep water in various parts of the 
world, the slender-clawed Willemcesia leptodactyla occurring in both the Pacific 
and Atlantic Oceans, at depths varying from thirteen hundred to over two thousand 
fathoms. As in many deep water species the eye-stalks are rudimentary. The 
five posterior pairs of thoracic limbs are chelate in both sexes, and the first pair of 
antennae have their inner branches long, while the carapace is flattish with a small 
rostrum. 
The remaining three families, namely, the Nephropsidce, or lobsters, the 
Potamobiidce, and Parastacidoe, or true crayfish, are nearly allied. Among the 
common crayfish (slightly reduced). 
former, the Norway lobster ( Nephrops ) is smaller than the common lobster, and 
has the pincers long, slender, and covered with scale-like tubercles. The common 
lobster ( Astacus gammarus), from a commercial point of view, is one of the most 
important Crustaceans. The crayfish ( Potamobiidce ), which live exclusively in fresh 
water, are very like small lobsters; the species known as Potamobia fiuviatilis 
being found in many streams in England. Throughout the day crayfish usually 
lurk under stones or the edge of banks, and creep out in the evening in search of 
food, which consists of worms, water-insects, small frogs or fish, and plants and 
roots of many kinds. During the winter they seek the shelter of crevices or 
