19. Front of head with a rounded lobe on each side; with four sections in 

 antennal flagellum; Family Scyphac^dae 

 Armadilloniscus Uljanin 

 (Actoniscus Hargcr) 

 Front of head with a horny tubercle on each side; with three sections in 

 antennal flagellum 



AUomscus Dana (of Family Oniscidae) 



GENERAL REFEP^CES 



Hatch, M. H. 1947. The Chelifera and Isopoda of Washington. Univ. of 

 Wash. Pub. in Biol, Vol. 10, No. 5. Pg. 155-274. 



Ortmann, A. E. 1918. Higher Crustaceans (Malacostraca). Chap. 25 in 

 Ward and Whipple's 'Tresh-water Biology". John Wiley 6? Sons. New 

 York. 



Richardson, H. 1900. Synopses of North American Invertebrates — The Isc 

 poda. Amer. Nat., Vol. 34. 



Richardson, H. 1905. Monograph of the Isopods of North America. Bull. 

 U. S. Nat. Museum, No. 54. 



Van Name, W. G. 1936. The American Land and Fresh'water Isopod 

 Crustacea. Bull. Amcr. Museum of Nat. History, Vol. 71. New York. 



The names used as first choice in the Isopod key are those given in Van 

 Name's Monograph. 



KEY TO THE PRINCIPAL GENERA AND SPECIES OF DECAPODS 



1. Carapace short and wide, much flattened dorso-ventrally, almost circular 



as view-ed from above; abdomen bent forwards under cephalothorax; 

 marine species, some of which may invade fresh water or occur on land 

 near the sea 

 Crabs 

 Carapace elongate, not so much flattened; abdomen extending backwards 



2. 



2. First two pairs of legs with opposing claws; mostly marine, but a few fresh' 



water species Shrimps and Prawns 3. 



First three pairs of legs with opposing claws; fresh- water species; Family 



Astacidae Crayfishes (Crawfishes, Crawdads, etc.) 6. 



3. With bunches of hairs on the ends of the claws; blind cave species; Ken' 



tucky; Family Atypidae 



Palaemon^as ganteri Hay Cave Shrimp 

 With scattered hairs on the claws; Family Palaemonidae 4. 



4. With palps on mandible; second legs of male very long, with large claws; 



large enough to be used for food; Ohio and Mississippi Rivers 

 Macrohrachium ohionis (Smith) Great Shrimp 

 (Palaemon ohionis Smith) 

 No palps on mandibles; claws of first two legs about equal; about one to 

 two inches long 5. 



191 



