REPORT ON THE BRACHYURA. 
275 
Subfamily 2. Hexapodina;. 
1 Asthenognathidx, Stimpson, Proc. Acad. Nat. Sci. Pkilad., p. 107, 1858, descript, nulla. 
Characters of Pinnotherinse, but the ischium of the exterior maxillipecles and the dactyli 
of the ambulatory legs are longer and more distinctly developed, and the ambulatory 
legs of the fifth pair, which are often short in Pinnixa, are altogether aborted or 
represented by a mere rudiment. 
Genera : — Hexapus, de Haan ; Amorphopus, Bell ; Thaumastoplax, Miers ; 
Asthenognathus, Stimpson, may belong to this group, but nothing is said 
with regard to the form of the fifth ambulatory legs, if developed ; 
Xenophthalmiis, White, which is somewhat intermediate between this group 
and the Pinnotherinae, differs from the genera of both groups in the form of 
the orbits, which are narrow, longitudinal and open above. 
Subfamily 3. Myctirinve. 
Carapace very convex, usually subglobose. Front rostrated ; rostrum deflexed. The 
exterior maxillipedes bulge out beyond the buccal cavity, and the merus and ischium 
joints are largely developed. Dactyli of the ambulatory legs styliform, well developed. 
This subfamily establishes the transition to the Ocypodidse. 
Genera : — Myctiris, Latreille ; Dotilla, Stimpson ( Doto , de Haan) ; Scopimera, 
de Haan. 
Subfamily 4. Hymenosomina;. 
Hymenosominx, Milne Edwards, tom. cit ., p. 221, 1853. 
Hymenicinx, Dana, tom. cit., p. 379, 1852. 
Carapace flattened on the dorsal surface, more or less, triangulate. Front rostrated. 
Ischium of the exterior maxillipedes and dactyli of the ambulatory legs well developed. 
Genera : — Hymenosoma, Desmarest ; Halicarcinus, White ( — Liriopea , Nicolet) ; 
Hymenicus, Dana ; Elamena, Milne Edwards ; Elamenopsis, A. Milne 
Edwards ; Trigonoplax, Milne Edwards ; Rhynchoplax, Stimpson. 
Subfamily 1. Pinnotherina:. 
Pinnotheres, Latreille. 
Pinnotheres, Latreille, Hist. Nat. Crust, et Ins., vol. vi. p. 78, 1803-1804. 
„ Milne Edwards, Hist. Nat. Crust., vol. ii. p. 30, 1837; Ann. d. Sci. Nat., ser. 3, 
Zool., vol. xx. p. 216, 1853. 
Pinnothera, Dana, U.S. Explor. Exped., vol. xiii., Crust. 1, p. 378, 1852. 
Body soft and membranaceous; carapace smooth, subglobose, the regions not defined, 
the lateral margins regularly arcuated ; orbits very small, usually nearly circular, with 
