68 



ON THE BRACHYFROUS DECAPODS OF THE CAPE. 



manibus articulo secundo intus quinque-dentato, chelis apice concoloribus ad marginem 

 baud striatis. 



Note. This beautiful little species is four lines long, by more than five broad. 



12. The above great number of Grapsidce at the Cape shews that the carcinology of South 

 Africa agrees with that of intratropical climates more than it does with that of the temperate 

 zones in general. But we now proceed to the stirps Pinnotherina, and for that purpose we 

 must return to the family Ocypodidce. Milne Edwards has shewn that a small crab of the 

 Red Sea, called by him Doto sulcatus, makes the passage from the Ocypodidce to the 

 Vinnotlierina. 



Stirps. PINNOTHERINA, Dehaan, or Parasitical Crabs. 



13. This stirps contains so few known species, that I shall not attempt its arrangement at 

 present, more particularly as Dr. Smith has only brought home one species, which has long 

 been known as a native of the Cape of Good Hope. M. Dehaan makes the distinguishing 

 characteristic of this stirps, which he calls PinnotJieridea, to consist in the sixth joint of the 

 fourth pair of maxillae being inserted at the base of the fifth joint. The groupe consists of 

 singular crabs, among which we find the last pair of feet to be sometimes evanescent, as in the 

 genus Hexapus of Dehaan. 



Fam. HYMENOSOMIDiE. 



Genus. HYMENOSOMA, Leach. 



Sub-genus. Leachium, M. E. 



Sp. 32. (Hymenosoma) Leachium orbiculai - Leach, MSS. 



Hymenosoma orbiculare, Desm. Cons. p. 163. tab. 26. fig. 1. 



Note. Milne Edwards has shewn that the Hymenosoma Leacliii of Guerin belongs to 

 another sub-genus. 



14. Perhaps when the attention of collectors shall have been more directed to these small, 

 though curious crabs, we may discover their natural arrangement. The difficulties pointed out 

 by Milne Edwards, who complains that his genera are so distinct from each other, evidently pro- 

 ceeds from almost every one of his genera belonging to a distinct family. Perhaps indeed, if we 

 consider his arrangement in this light — in other words, that most of his genera represent fami- 

 lies—the table he gives (vol. 2, p. 29) may not be found so far wrong. But however this may 

 be, I shall now return to the stirps Cancrina and family Carcinidce. From these we pass 

 directly to the osculant stirps Corystina, belonging to the interesting tribe of Trigonostomous 

 Brachyura, which may be displayed to view in the following manner : — 



