THE CRUSTACEA OF NEW JERSEY. 379 



This great group includes, as the above caption would signify, 

 the short-tails or true crabs, typified by those forms known popu- 

 larly as crabs, in distinction to the shrimps, crawfishes and lob- 

 sters, or the long-tails. In this division the Crustacea attain their 

 most specialized development, indicitave of most every feature 

 of adaptation. A vast assemblage of genera and species is thus 

 embraced in this connection, which is rather poorly represented by 

 the littoral shore forms of New Jersey waters. 



Kev to the tribes. 



a. Carapace usualy trianguar. with pointed or spinous protruding rostrum., 



OXYRHYNCHA. 



aa. Carapace not usualh' triangular, without pointed or protruding rostrum. 



b. Buccal frame usually triangular, narrowed forward : efferent channels 



opening at middle of endostome. i.Eucosoidea. 



bb. Buccal frame quadrate ; efferent branchial channels opening at sides 



of endostome. 



c. Carapace not quadrilateral, but short, broad, rounded anteriorly ; 



verges of male inserted in basal joints of fifth pair of legs. 



CANCROIDEA. 



ci-. Carapace usually quadrilateral ; frontal region curved downward ; 

 verges of male inserted either in sternal plastron or in basal 

 joints of fifth pair of legs, thence passing through channels in 

 sternum beneath abdomen. gr.a.psoidea. 



Tribe O.xyrhyncha. 



The Spider Crabs. 



Carapace narrowed anteriorly, rostrate, with hepatic regions 

 small and l)ranchial large. Epistome generally large. Buccal 

 frame quadrate, with anterior margin straight. Branchiae in 

 nine pairs, with efferent channels opening at sides of endostome 

 and afferent channels opening behind pterygostomian regions 

 in front of bases of chelipeds. First antenncT longitudinally 

 folded. Third maxillipeds with fifth joint articulated at apex 

 or at front inner angle of fourth. Genital organs, in male, 

 inserted at bases of last pair of trunk legs. 



