THE CRUSTACEA OE NEW JERSEY. 311 



ternal at base of endopodite. Genital ducts never open on 

 sternum. Except in very few forms, those for most part small 

 pelagic and nectic species, fourth and fifth pairs of thoracic legs 

 not reduced in size, nor ever folded within branchial chambers. 

 A very large group, comprising familiar forms as shrimps, 

 crawfish and lobsters, etc. The following classification is adopted 

 largely from Alcock. 



Key to the Tribes. 



a. Body and rostrum generally compressed ; carapace not impinging upon 

 epistome antero-laterally ; abdomen usually dorsally elbowed or humped; 

 pleura of first abdominal somite seldom reduced; antennal scale almost 

 always large and foliaceous so as entirely concealing antennal peduncle. 



CARIDIDES 



aa. Body and rostrum not particularly compressed, sometimes decidedly de- 

 pressed ; carapace impinges on or articulates with, or fuses with, epistome 

 antero-laterally; abdomen not humped; pleura of first abdominal somite 

 reduced ; antennal scale present or absent, in former case foliaceous or 

 spiniform, and if foliaceous not concealing terminal joint of antennal 

 peduncle entirely. astacidES 



Trihe Caridide^. 



Body generally compressed. Rostrum generally compressed. 

 Integument very rarely strongly calcified. Abdomen symmetri- 

 cal, long, bent or humped. Telson usually acute, occasionally 

 bluntly rounded. Pleura of last abdominal somite little or not 

 reduced. Basal joint of antennular peduncle usually with spine 

 or scale (stylocerite) at proximal end of outer margin. Olfac- 

 tory setse confined to proximal end of outer antennular flagel- 

 lum. Antenna! scale mostly large, entirely conceals and projects 

 far beyond antennal peduncle. External maxillipeds pediform 

 and mostly longer than first pair of thoracic legs. Thoracic legs 

 consist usually of seven movable joints, first two or three pairs 

 may be chelate and last two never truly so, all five pairs often 

 very slender or first, second or third may be enlarged or massive, 

 and fourth and fifth pairs occasionally (Sergestidse) rudimentary 

 or absent, but never folded in branchial chamber. Abdominal 

 appendages well developed, first pair often biramous. Male 



