536 CRUSTACEA— ORDER DEC APOD A. 



Sub-Order III. — Schizopoda. 



These are slender shrimp-like Oruskicea, with a large soft shield covering 

 the cephalothorax, and even part of the abdomen. The legs and giU-feet are 

 bifid, and similarly formed. They swim in large shoals in the open sea, and 

 are among the numerous surface-animals which form the food of whales. 



Order III. — Decapoda. 



This extensive order is the most important among the Ci-vdacea. The 

 species which it includes have a hard calcareous shield, which generally covers 

 the head and thoracic segments, as well as more or less of the abdomen. 

 Under this shield lie the gills. There are two faceted stalked eyes, between 

 which frequently projects a strong spine. They have usually three pairs of 

 jaws, three pairs of thoracic gill-feet, and five pairs of walking legs, from 

 which they derive their name. They may be divided into three sub-orders 

 — the Macrura, or lobsters, prawns, and shrimps ; the Anomura, or hermit 

 crabs ; and the Brachyiira, or crabs. 



Suh-Ch-der I. — Macrura. 

 In the Macrura the abdomen is largely developed, and the first five (or 

 more rarely, four) segments bear walking legs. There is a large flattened 

 triple fin at the extremity of the abdomen, formed by the terminal segment, 

 and a leaf-like appendage attached on each side to the one preceding. 



The Graiigonidm are moderate-sized Orustacea with semi-transparent bodies, 

 a thin horny carapace, the outer antennas with a large moveable scale at the 

 base, and sometimes a very strong ridged spine between the eyes. The first 

 three pairs of legs are generally chelate (pincer-like). The 

 Shrimps and species generally live in shoals in shallow water, near. the 

 Prawns. shore, where they are captured by waders in specially-con- 



structed nets. Most of the species are marine, such as the 

 shrimps and prawns ; some are found in fresh water lakes and rivers ; and 

 one or two blind species in caves. Some species, in which the skeleton is 

 universally soft, inhabit the large shells of the Pliiiia. 



The Astacidm are large hard-shelled species, with a small scale at the base 



of the outer antennte. The first pair of legs is developed into great claws. 



The gills are numerous ; sometimes there are as many as 20 pairs. They 



inhabit the sea, where they live in clefts among the rooks ; and other species 



are found in lakes and rivers, where they live in holes in the banks. The 



two representative species of this family are the lobster and 



Lobsters. the river crayfish. Some years ago a detailed monograph on 



the crayfish was published by the late Prof. Huxley, to which 



those who wish to study the anatomy of a Crustacean can easily refer. 



The crayfish forms a very important article of diet in Eastern Europe, and is 



recorded in the Esthonian ballads to have formed the principal article of food 



of their mythical hero, the Kalevi poeg, when he retired to a 



Crayfish. hermitage on the banks of a river, after a disastrous war. 



He used a tall fir-tree torn up by the roots, as an angle, and 



baited it with the body of a dead mare. (See my "Hero of Esthonia," i., p. 



