1852.] 9 



armatis, paris postici apice setis longiusculis instructis. "Typus est Monolepis 

 spiiiitarstiSy Say. Hie pertineret quoque Meg. rmitica,'De%m. si ejus pedes postici 

 setis longiusculis confecti ; aliter genus alterum instituendura. Verbunn *' Ma- 

 restia" clarissimum Desmarest connmennorat. 



3. Megalopa, Leach. Carapax fronte simpliciter rostratus, rostro vix 

 deflexo, acuto. Pedes 8 postici ad basin infra uni-spinigeri : 5ti minores, tarso 

 styliformi. ^Typus Meg. Mo7itagui, Leach.* 



4. Cyllene, Bana, Carapacis frons uti in Megalopa. Pedes 8 postici ad 

 basin infra uni-spinigeri ; 5ti minores, tarso anguste lamellato, setis longiusculis 

 partim ciliato. 



5. Tribola, Dana. Carapax fronte horizontalis tricuspidatus, rostro (vel 

 cuspide mediana) tenui, cuspidibus (vel dentibus) externis vix longiore. Antennae 

 internae inter rostrum et cuspides externas aperte inflexae. Pedes postici minorefly 

 tarso unguiculato setisque longis non instruct. 



Descriptiones Megalopideorum adhuc ineditcB, 



Marestia elegans. Carapax antice angustus et superne visus bilobatus, late- 

 ribus fere parallelis, pone oculos vix salientibus. Pedes antici parvi, manu 

 oblonga, margine inferiore et partim superficie interna remote hirsutis. Pedes 

 2di marginibus sparsim ciliati, tarso infra V-spinoso, ad basin tuberculum infra 

 non gerente. Tarsi postici infra 6-spinosi, apice unguiculati et 4 setis longis 

 instructi. Ba5. Promontorio Bonae Spei. Il07^^. Carapacis 4 5'^\ An Megalopa 

 mutica Kraussii (Sddaf. Crust, p. 54) et De Haanii (Faun. Japon. p. 167) ? Sed 

 pedes postici extremitate setis tarso paulo longioribus instructi. 



Marestia Atlantica. Carapax antice angustus et superne visus bilobatus, 

 lateribus postice paulo divergentibus, pone oculos vix salientibus. Pedes an- 

 tici parvi, manu oblonga, nuda aut nudiuscula. Pedes 6 sequentes nudiusculi, 

 tarso infra quinque spinas tuberculumque ad basin instar calcis gerente. 

 Tarsi postici parvuli, sed setularum duabus paribus infra instructi, non spinosi, 

 apice unguiculati et tribus setis longis armati. Hab. lat. aust. 6^, long. occ. 24**. 



Marestia pervalida. Carapax antice latus et superne visus obsolete quadri- 

 lobatus, lobis subasquis, lateribus postice non divergentibus, prope medium uni- 

 dentatis. Pedes antici pervalidi, manu valde crassa, tumida. Tarsi postici 

 infra spinosi, apice tribus setis longiusculis armati. Hab. lat. bor. 6, long, 

 orient. 173. 



Monolepis oRiENTALis. Sterni segmenta fossam sterni includentia antica mar- 

 gine interiore fere truncata, vix triangulata ; segmenta proxima convexa, non tu- 

 berculigera. Tuberculus medianus inter aream buccalem et fossam sterni simpli- 

 citer subtriangulatus, antice acutus, postice hemisphericus, utrinque depressione 

 deinde septo brevi antice et oblique producto cinctus. Tarsus pedis postici 

 brevis, non unguiculatus, apice tribus setis longiusculis armatus, infra setulis 

 paucis perbrevibus necque spinis instructus. Hab. in mari Suluensi. Long. 

 carapacis 4.'". M. inermis differt, sterni segmentis anticis intus non subtruncatis 

 sed prominenter triangulatis, proximis unituberculatis, tuberculo mediano inter 

 aream buccalem et fossam sterni tuberculis tribus composito.f 



Cyllene hyalina. Rostrum parce prominens. Carapax subovatus, lateribus 

 pone oculos paulo saliens, postice inermis. Thorax infra ad extremitatem pos- 



* Malac. Pod. Brit, pi. 16. Leach describes three other species, (not noticed bf 

 Edwards,) in Tuckey's Exped. to the Zaire, (London, 1818,) p. 404. The M. 

 Cranchii may be a true Megalopa ; the others have a deflexed beak. 



tThe author is indebted to Prof. L. R. Gibbes, of Charleston, S. C, for the 

 privilege of examining specimens of the M. inermis. They were obtained by him 

 from the stomach of a fish off the Atlantic coast between New York and Charleston, 

 in 1846. See Rep. Crust, in U. S. Collections, by Prof. Gibbes, in Proc. Amer. 

 Assoc. Charleston, 1850, vol. iii; p. 192. 



2 



