GRAPSOIDEA. 



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

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



2. SESARMINiE. — Antennae internaa fronte tectaa, Articulus 

 maxillipedis externi otius costa obliqua in 2dum producta notatus. 



1. Articulus maxillipedis externi Stius apice rotundatus. 



G. 1. Sesarma, Say* — Carapax quadratus, saepe partial lineolatus, lateribus 



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



angustius. Tarsi saepe armati. 

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



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



Tarsi inermes. 



2. Articidus maxillipedis externi Stius apice truncatus scepeque excavatus. 



G. 3. Cyclograpsus, Edio.-f — Carapax lasvis, medio planus, ad margines ante- 

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

 contiguo vix angustius. 



G. 4. Chasmagnathus, Be 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, Be JI.§ — Carapax quadratus, lateribus parallelis, rectis. Oculi 

 longiusculi. Abdomen maris versus basin sterno contiguo multo angustius. 



3. PLAGUSINJ5.— Antennas internas sinubus frontis longitudinalibus 

 apertae. 



G. 1. Acanthoptjs, Be IL\\— Corpus valde depressum. Articulus maxillipedis 



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



lmi internus apice angustus et non transversus. 

 G. 2. Plagusia, Latr.,^ B. — Corpus minus depressum, crassius. Articulus 



maxillipedis externi 3tius apice 2di vix angustius, raro longior quam latus. 



Ramus maxillipedis lmi internus apice transversus. 



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

 f Crust., ii. 77.— Gnathochasmus 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. 

 Tf Corresponds to Plagusia and Philyra of De Haan, Faun. Japon., p. 31. 



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