THE CRUSTACEA OF NEW JERSEY. 167 



Key to the tribes. 



a. Abdomen rudimentary ; first thoracic segment fused with head : forms 



of aberrant structure. capreli,idE.\ 



aa. Abdomen well developed ; head and eyes generally not of unusual size ; 



maxillipeds with palps. gammaridEa 



Tribe CaprELLIDEa. 



Head fused with first segment of thorax. Abdomen rudi- 

 mentary. Second gnathopods larger than first. Usually gills 

 present only on third and fourth segments of thorax. Anterior 

 pairs of per?eopods usually wanting". No pleopods. Uropods 

 rudimentary or wanting. 



Family CAPRELLID^. ] 



The Skeleton Shrimps. 



Body narrow, cylindric, \'ery flexible, last segment of meso- 

 some generally defined from cephalon by slight dorsal depres- 

 sion, third and fourth segments in female much broader than 

 in male, and carrying marsupial pouch. Superior antennae slen- 

 der and elongated, with multiarticulate fiagellum. Inferior an- 

 tennae w^ell developed, though usually much smaller than superior. 

 Buccal area rather prominent. Anterior lip broad, bilobed. 

 Posterior lip with distinct inner lobes. Mandibles with or 

 without palps. First pair of maxillae without any basal 

 lobe, palp well developed, biarticulate, and second pair small. 

 Maxillipeds normally developed, with large pediform palps. 

 Gnathopoda very unequal, anterior comparatively small and 

 originating far in front, beneath cephalon, and posterior much 

 larger and often very differently shaped in both sexes. 

 Perasopoda more or less reduced in number, two posterior pairs 

 always strongly developed and prehensile. Metasome and uro- 

 some forming together generally very small nodi form appendage 

 issuing betw-een bases of last pair of peraeopoda, and carrying 

 more or less distinct rudiments of limbs (uropoda). 



