LOBSTERS, CRAYFISH, ETC 



267 



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 Willemiesia 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 

 antennas have their inner branches long, while the carapace is flatfish with a small 

 rostrum. 



The remaining three families, namely, the NephropsidcB, or lobsters, the 

 Potamobiidce, and Parastacidw, 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 (Potamobiidm), 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 mid 

 roots of many kinds. During the winter they seek the shelter of crevices or 



