THE CRUSTACEA OF NEW JERSEY. 199 



Key to the genera. 



a. Terminal uropods uniramous. ericthonius 



aa. Terminal uropods biramous. ampithoe; 



Genus Ericthonius Milne-Edwards. 



Ericthonius Milne-Edwards, Ann. Sci Nat. Zool., XX, 1830, p. 382. Type 



Ericthonius diiformis Milne-Edwards, monotypic. 

 Erichthonius, auct. 

 Cerapodina Milne-Edwards, Hist. Nat. Crust. Ill, 1840, p. 62. Type Cerapus 



abditus Templeton, monotypic. 

 Dercothoc Dana, Amer. Journ. Sci. Art., (2) XIV, 1852, p. 313. Atypic. 



(Type Gammarus emissitius Dana, first species in Crust. U. S. Expl. 



Exped., 1852, p. 968.) 

 Pyctihts Dana, Amer. Journ. Sci. Art., (2) XIV, 1852, p. 313. Atypic. (Type 



Erichthonius macrodactyhis Dana, first species in Crust. U. S. Expl. 



Exped., 1852, p. 973.) 



Body slender, snbdepressed, with very small coxal plates, of 

 which anterior pairs larger than posterior, and epimeral plates 

 of metasome small. Urosome narrow, elongated. Cephalon 

 with frontal part considerably produced, lateral lobes tumid and 

 more or less projecting. Eyes well developed, placed within 

 lateral lobes of cephalon. Antennae slender, subequal, edged 

 posteriorly with fascicles of slender bristles, superior ones with- 

 out an accessory appendage, inferior ones issuing at considerable 

 distance behind superior, and with antepenultimate joint of 

 peduncle unusually elongated. Flagella of both pairs of antennae 

 multiarticulate. Anterior lip produced in front to an acuminate 

 projection, and posterior lip with well-defined inner lobes. Man- 

 dibles short and stout, with palp much elongated, and terminal 

 joint lamellar and densely setiferous. Alaxillae normal. Max- 

 illipeds with palps comparatively narrow. Gnathopoda very un- 

 equal, anterior ones rather small and of similar structure in two 

 sexes with carpus comparatively large and lamellarly expanded 

 below, propodus short but broad, nearly triangular in form. 

 Posterior gnathopoda in female considerably larger than an- 

 terior, carpus produced below to setiferous lobe, propodus rather 

 expanded with palm well defined. In male posterior gnathopoda 

 of enormous size, complexly chelate, carpus exceedingly large 



