CRUSTACEA OF ALABAMA. 53 



Fam. Lysianassid/E. Upper antennas with a short secondary flagellum, only the first foot chelate, body 

 little compressed. ..... Genus Pontoporeia. 



VIII. Order Isopoda. 



Fam. Oniscid/e. Inner pair of antenna; obsolete, madible not palpate, last abdominal segment small. 



Genus Porcellio, Etc. 

 Fam. Asselid^e. Inner pair of antennae short, lower long, mandible generally with a palp, last abdom- 

 nal segment large. 



1. First pair of feet chelate, caudal stylets elongate, mandiblar palp absent. 



Genus Mancasellus. 



2. As above, palp present. ..... (page 39) Genus Asellus. 



IX. Order Brachyiira. 



A. Large or medium sized aquatic crabs. 



a. Posterior pair of limbs, paddle-like, for swimming. 



1. Lateral margins of shell [carapace] extended into strong spine, carapace wider than long. 



(page 42) Genus Callinedes. 



2. Carapace not much broader than long, lateral margins not generally produced. 



(page 43) Genus Platyonichus. 



b. Posterior pair of limbs like the others. 



1. Of large size, carapace oval, .... (page 42) Genus Menippe. 



2. Rather small, carapace subpentagonal. . . . (page 42) Genus Panopeus. 



B. Small crabs living in gasteropod shells. ..... Genus Eupagurus. 



C. Small crabs, not strictly aquatic. 



1. One of the male claws [chelae] greatly enlarged. . (page 44) Genus Gclasimus. 



2. Male chela; alike or nearly so. ... . (page 43) Genus Sesarma. 



X. Order Macroura. 



Fam. Astacid/e. Abdomen not laterally compressed, carapace with a transverse channel, united with 

 the epistoma, gills filamentous, three pairs of feet chelate, the first being largest, 

 rostrum flattened from above. . . . (page 47) Genus Cambarus. 



Fam. Penaeid/E. Abdomen laterally compressed, carapace with no transverse channel, three pairs of feet 

 chelate, the first not greatly enlarged, rostrum generally laterally compressed, ser- 

 rate. . . ... - . (page 46) Genus Penceus. 



Fam. Pal^monid^e. Abdomen laterally compressed, carapace unchanneled, gills composed of plates, 

 third pair of feet not chelate, rostrum generally laterally compressed, serrate. 



1. Rostrum short. ... ... (page 47) Genus Crangon. 



2. Rostrum long, laterally compressed, mandible with a three jointed palp. 



(page 45) Genus Palcemon. 



3. Rostrum as above, mandible not palpate. . . (P a g e 45) Genus Palcemonetes. 



