GRAPSOIDEA. 333 



Frons sursuin sinuosus, antennis internis obliquis, in plicis frontis insitis. Arti- 

 culus maxillipedis externi 3tius suborbiculato-cordatus. Tarsi inermes. 



2. SESARMIN^E. Antennas internse fronte tectae. Articulus 

 maxillipedis externi 3tius costa obliqua in 2dum producta notatus. 



1. Articulus maxillipedis externi Stius apice rotundatus. 



G. 1. SESARMA, Say.* Carapax quadratus, saepe partim lineolatus, lateribus 



rectis, fronte recte prserupto. Abdomen maris versus basin sterno contiguo vix 



angustius. Tarsi ssepe armati. 

 G. 2. SARMATIUM, Dana. Carapax subquadratus, lateribus arcuatis, fronte cur- 



vatim declivi. Abdomen maris versus basin sterno contiguo vix angustius. 



Tarsi inermes. 



2. Articulus maxillipedis externi Ztius apice truncatus scepeque excavatus. 



G. 3. CYCLOGRAPSUS, Edw.-\ Carapax laevis, medio planus, ad margines ante- 

 riores declivis, lateribus arcuatis, integris. Abdomen maris versus basin sterno 

 contiguo vix angustius. 



G. 4. CHASMAGNATHUS, De H.\ Carapax convexus, subquadratus, lateribus ar- 

 cuatis et antice emarginatis, fronte curvatim declivi. Oculi breves. Abdomen 

 maris versus basin sterno contiguo parce angustius. 



G. 5. HELICE, De //. Carapax quadratus, lateribus parallelis, rectis. Oculi 

 longiusculi. Abdomen maris versus basin sterno contiguo multo angustius. 



3. PLAGUSIN J3. Antennae internae sinubus frontis longitudinalibus 

 apertas. 



G. 1. ACANTHOPUS, De If. || Corpus valde depressum. Articulus maxillipedis 



externi 3tius oblongus, parvus, apice 2di multo angustior. Rainus maxillipedis 



Imi internus apice angustus et non transversus. 

 G. 2. PLAGUSIA, Latr.f\ D. Corpus minus depressum, crassius. Articulus 



maxillipedis externi Stius apice 2di vix angustius, raro longior quam latus. 



Ramus maxillipedis Imi internus apice transversus. 



* Jour. Acad. Nat. Sci., i. 76, 1817. Pachysoma of De Haan, Faun. Japon., p. 33. 

 f Crust., ii. 77. Gnathoehasmus of M'Leay, Smith's Illust. Zool. S. Africa, and Cat. 

 Crust. Brit. Mus., by A. White, 1847, 40. 

 J Faun. Japon., p. 27. 

 Faun. Japon., p. 28. 



|| Faun. Japon., p. 29. Corresponds to Plagusia clavimana. 

 1 Corresponds to Playusia and Philyra of De Haan, Faun. Japon., p. 31. 



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