DECAPOD CRUSTACEANS OF THE BEAUFORT, N. C, REGION. 375 



KEY TO THE FAMILIES OF DECAPOD CRUSTACEANS WHICH ARE REPRESENTED IN THE BEAUFORT REGION. 



o. General form shrimplike — the abdomen well developed and, usually, with the cephalothorax also, 



compressed; pleopods always present in full number and used for swimming. (Suborder Nataniia). 



b. Pleura of second segment of abdomen not overlapping those of the first segment . . (Tribe Peneidea). 



c. First three pairs of legs chelate ; all of the legs well developed Family PeneiD/E (p- 377). 



cc. None of the legs chelate ; last two pairs of legs small or wanting. . . .Family Sergestid.® (p. 381). 

 66. Pleura of second segment of abdomen overlapping those of the first segment. . . . (Tribe Caridea). 

 c. Carpus of second pair of legs subdivided into two or more articles. 

 d. Eyestalks short and usually covered by the carapace; first pair of legs stronger than the 



second pair Family Crangonid^E (p. 382). 



dd. Eyestalks of medium length or long, not covered by the carapace ; first pair of legs not stronger 

 than the second pair. 

 e. Rostrum small or wanting; eyestalks very long and slender; first two pairs of legs 



subequal Family Ogyrid.E (p. 388). 



ee. Rostrum well developed; eyestalks not abnormally lengthened; second pair of legs usually 



longer or stronger than first pair Family Hippoi.ytid.iE (p. 390). 



cc. Carpus of second pair of legs not subdivided. 



d. Rostrum well developed and compressed; first pair of legs not subchelate. 



e. Third pair of maxillipeds pediform; body slender Family Pal.Emonid.E (p. 392). 



ee. Third pair of maxillipeds very broad ; body short and thick . Family GnaThophyllid.E (p. 395) . 



dd. Rostrum short; not compressed; first pair of legs subchelate Family Cragonid.E (p. 396). 



aa. General form lobsterlike or crablike — the abdomen may be well developed or greatly reduced in 

 size, but in either case it, and, usually, the cephalothorax also is depressed; pleopods reduced 



or absent, not used for swimming (Suborder Reptantia). 



b. Abdomen extended, symmetrical, well armored, with well-developed pleura and broad tail fin; 

 third pair of legs like the first, either chelate or simple; branchiae numerous. 

 c. Rostrum small or wanting; exopodites of uropods not sharply divided into two parts 



(Section Palinura). 

 d. Bodysubcylindrical; antennae with strongly developed flagella. . Family Paunurid/E (p. 398). 



dd. Body strongly depressed; antennae short, squamiform Family ScyxlaiudjE (p. 398). 



cc. Rostrum well developed; exopodites of uropods divided into two parts by a suture 



(Section Astacura). 

 d. Marine species; last segment of thorax coalesced with the one in front of it 



Family Homarid.e (p. 399). 

 dd. Fresh -water species; last segment of thorax not coalesced with the one in front 



of it Family Astacid^E (p. 400). 



66. Abdomen bent upon itself or flexed beneath the thorax, or, rarely, soft and extended; pleura 



usually small or wanting; third pair of legs unlike the first, never chelate; branchiae usually few. 



c. Uropods usually present, often reduced in size, sometimes united with the telson; last thoracic 



sternum free ; carapace not fused with the epistome (Section Anomura) . 



d. Abdomen well developed. 



e. Abdomen symmetrical; tail fan well developed. 



/. Abdomen more or less flexed beneath the thorax; body depressed. Tribe Ga/a/te'rfea. 



g. Form somewhat lobsterlike; rostrum well developed. . .Family Gai,atheid.E (p. 401). 



gg. Form crablike; rostrum short and broad or wanting. Family Porcellanid^ (p. 403). 



ff. Abdomen extended, more or less membranous; cephalothorax compressed (Tribe 



Thalassinidea) Family Caluanassid^ (p. 406). 



ce. Abdomen tinsymmetrical ; tail fan reduced and adapted for holding the body in hollow 



objects. (Tribe Paguridea) Family Pagurid/E (p. 408). 



dd. Abdomen much reduced in size and flexed under the thorax; tail fan not adapted for swim- 

 ming; rostrum small or wanting (Tribe Hippidea). 



e. First pair of legs simple; carapace subcylindrical Family H1PPID.E (p. 416). 



ee. First pair of legs subchelate; carapace depressed Family Albuneid^ (p. 414). 



cc. Uropods rarely present, never biramous; abdomen small and permanently flexed beneath the 

 thorax; first pair of legs always chelate or subchelate (Section Brachyura). 



