228 REPORT OF XEW JERSEY STATE MUSEUM. 



with apical sensory appendages short, papilliform. Antennce 

 usually slender, with flagellum pauciarticulate. Buccal mass 

 not very prominent below. Mandibles With cutting part highly 

 chitinized and as usual of two superposed dentate lamellce, be- 

 hind which a membranous hairy lappet and varying number of 

 pencils, molar expansion obsolete, without any triturating sur- 

 face, it replaced by brush-like recurved seta. Anterior maxillse 

 with outer masticatory lobe very strong and coarsely spinous at 

 tip, inner lobe much narrower, with only two hairy bristles. 

 Posterior maxillae distinctly bilobed at tip, with outer edge angu- 

 larly produced near base. Maxillipeds with basal part broad 

 and laminar, though scarcely expanded distally, terminal part 

 poorly developed and never composed of more than three joints, 

 last very narrow. Masticatory lobe short, truncate near tip. 

 Epignath large, flanking basal part. Legs usually slender, in- 

 creasing in length posteriorly. Sexual appendage of male simple, 

 conic, generally connected with inner rami of first pair of 

 pleopoda Latter very largely developed, ending each in highly 

 chitinized conical joint, obliquely grooved below, for conducting 

 evacuated sperm. Inner ramus of second pair of pleopoda in 

 male end in slender lash finely pointed at tip. Uropoda with 

 outer ramus more or less flattened, lanceolate, inner much 

 smaller, sublinear, and usually attached far in front of outer. 



Key to the genera. 



0. 'External opercular ramus of first and second pairs of abdominal append- 

 ages furnished with tracheae, flagellum of external antennae biarticulate. 



PORCELLIO. 



aa. External opercular ramus of abdominal appendages contains no special 

 respiratory organ ; flagellum of external antennae triarticulate. 

 h. Epimera of thoracic segments small ; abdomen abruptly narrower than 

 thorax : first two segments generally equal in length those following, 

 and very small epimera manifest. philoscia. 



bb. Epimera of thoracic segments large, with all posterior angles acute ; 

 abdomen not abruptly narrower than thorax; first two abdominal seg- 

 ments very short, three follownig ones large, with large acute epimera. 



ONISCUSt 



