268 CRUSTACEA. 



Again, the hexagonal Lnpas have the second, third, and fourth legs 

 very slender ; moreover, the short and large eyes, which are not con- 

 cealed when retracted, give the crab a staring look. These charac- 

 ters, in connexion with the narrow form, and the transverse front 

 making an angle with the sides, show that they are a distinct group, 

 and belong together, although varying so widely in the outer maxil- 

 lipeds, as mentioned on page 74. As in the genus Lupa, these species 

 may have either a short or a long lateral tooth or spine, this distinc- 

 tion not being of generic importance. 



But Oceanus is hardly distinct from Charybdis, and Charybdis 

 graduates into Thalamita. 



The peculiar character of the Lupa cribraria, mentioned on page 

 62, requires for it a distinct genus and family. 



The Platyonychidae are distinct from the Portunidae, not only in the 

 absence of the ridge on the praelabial plate, but also in the absence 

 of the inner lobe to the inner branch of the first maxillipeds ; and 

 besides, the first joint of the outer antennas is moveable and subcylin- 

 drical like the following joint. 



The genera of Portunidas which appear to stand on good characters 

 are the following. We have doubt as to its being well to separate 

 Charybdis and Thalamita, as the transitions closely unite them, and 

 their characters are essentially the same. 



1. LUPIN^E. Sutura sterni mediana tria segmenta intersecans. 

 Palati colliculi prominentes. 



1. Pars antennae externse mobilis hiatu orbilas non occlusa, in orbitdjacendo aptata. 



G. 1. SCYLLA, De Haan.* Valde latus et crassus, marginibus anterioribus simul 

 sumtis bene arcuatis, antero-laterali Ipngiore quam postero-lateralis. Pedes 

 antici breviores, crassissimi, manu valde tuinida, non angulata nee prismatica. 



G. 2. LUPA, Leach.'f Valde latus, marginibus anterioribus totis simul sumtis 



bene arcuatis. Manus elongate trigona aut prismatica, costata. 

 v G. 3. AMPHITRITE, De Haan,$ Dana. Angustior. Margines frontalis antero- 



* Faun. Japon., 11. 



f Neptunus, Pontus, and Aclielous of De Haan (Faun. Japon., 8, 9), the distinctions 

 between which genera appear not to be sustained. 



J Faun. Japon., 8. Includes, as here adopted, the Lupa of De Haan, which division 

 he restricts to the Lupa forceps (Edw. Crust., i. 456). The Lnpocyclus of Adams and 

 White (Crust. Voy. Samarang, 46, pi. 12, f. 4), appears to be identical with Amphi- 

 trite. 



