DECAPODA 389 



FAMILY CALLIANASSIDAE. 



With the characters given above: about 7 American genera. 



1. CALLIANASSA Leach. Cuticula soft and smooth; first 2 pairs of 

 periopods chelate, the first pair being large and very unequal in size ; eye 

 stalks flattened; third pair of maxillipeds flattened: about 20 species, 6 

 American. 



C. stimpsoni S. I. Smith. Length 6 cm.; 

 small cheliped about half as long as the large 

 one; carapace smooth and glossy: from Long 

 Island Sound southwards, in burrows in the 

 mud between tide lines and in shallow water. 



2. GEBIA Leach. Cuticula soft and smooth ; Fig. 622 oeUa 

 forward portion of cephalothorax compressed, 



with a triangular, hairy rostrum; second pair of periopods not chelate; 

 third pair of maxillipeds pediform: 10 species, 2 American. 



Cr. affinis Say (Fig. 622). Length 10 cm.: Long Island Sound to 

 South Carolina, living in burrows in the mud between tide lines and in 

 shallow water. 



TRIBE 3. ASTACIDEA. 



Lobsters and crayfish (Sig. 623). Body of moderate or large size 

 and with a thick shell; first antennae with 2 flagella, second either with a 

 scale or with none and much longer than the first; no longitudinal 

 sutures, but usually a transverse cervical suture in the carapace: 4 

 families and about 150 species. 



Key to the families of Astacidea here described : 



di Antennal scale and cheliped present. 



6 X Animals marine 1. NEPHROPSIDAE 



5 2 Animals in fresh water 2, ASTACIDAE 



a a Antennal scale and cheliped absent 3. PALINUHTDAE 



FAMILY 1. NEPHEOPSIDAE. 



Lobsters. Body of large size; rostrum dentate along the lateral 

 margins; first 3 pairs of periopods chelate, the first pair very large, 

 forming the pinching claws: 3 genera. 



HOMARTJS Milne-Edwards. Rostrum with 3 teeth on each side; sec- 

 ond antennae with a small scale; eyes round: 2 species. 



H. americanus* M.-Ed. American lobster. Length up to 60 cm.; 

 greatest weight 13 kg. or over 28 pounds; length of the average adult 

 lobster 25 cm.; average weight less than a kg. or about one and three- 

 quarters or two pounds; color usually dark green with darker spots and 



* See "The American Lobster," etc., by F. H. Herrick, Bull. U. S. Fish. Com. for 

 1895. "Natural History of the American Lobster," by same, Bull. Bureau Fish., Vol. 

 29, p. 149, 1909. 



