ON THE BRACHYUROUS DECAPODS OF THE CAPE. 69 



Tribe. TRIGONOSTOMA. 



J^External antennae long. Hind feet of the more usual struc- 

 ]^ ture, and serving for locomotion. Oral orifice triangvdar, 



r External antennae long. Hind feet raised up over the 

 ■i back and serving for organs of prehension. Oral orifice 

 L triangular. 



fExternal antennae moderate. Hind feet raised up over 

 the back and serving for organs of prehension. Oral 

 I. orifice not alvrays triangular. 



^^Anterior feet not elevated into a crest. No branchial 

 1^ afferent apertures in front of the fore feet. 



J Anterior feet compressed and elevated into a crest. Bran- 

 1^ chial afferent apertures in front of fore feet. 



15. From the Corystina we pass to the Calappina, by means of Matuta. By Oreophorus we 

 leave the Calappina for the Leucosina. The passage from the Leucosina to the Dromiina is 

 not so clear ; but these last are close to the Doripplna, which last again are approximated 

 naturally to the Corystina, Still the tribe has never been worked out, and I think it more 

 than- possible that the Dromiina which I have here considered to be an aberrant groupe of 

 Trigonostomous Brachyura, will, in the end, be found to be an aberrant groupe of Anomurous 

 Macroura. Nay, this last is the position assigned to it by Milne Edwards, and the arguments 

 for such a location of Dromiina are their rudiment ^ abdominal appendages, and the oral orifice 

 being rarely triangular. On the other hand, however, they differ from all Macroura in having 

 fossulse for the reception of their internal antennse. The question therefore of their true place can 

 only be determined when the groupe shall have been worked out, which I fear cannot be done at 

 present, on account of the paucity of species which are known to belong to this essentially tropical 

 tribe. One thing, nevertheless, is established, namely, that the Dromiina are osculant, or, in other 

 words, they stand on the limits of the Trigonostomous Brachyura and Anomurous Macroura. 

 Into which of these circles the stirps truly enters, must be left for future investigation ; but 

 I shall provisionally consider it as belonging to the Brachyura. As for the families of 

 Trigonostomous Brachyura, I shall not at present attempt to indicate them, but proceed at 

 once to characterize the sub-genera brought from the Cape, which are only three. 



Stirps. CORYSTINA. 



Of the stirps Corystina we have no species from the Cape ; but the following is very close 

 to it, being aberrant in the next stirps. 



Aberrant Groupe. 



Macrocbra. 

 External antennae long, or at 

 least conspicuous. 



[ 1 Corystina. 



■4 2 DORIPPINA. 



L3 Dromiina. 



Normal Groupe. 



Brachycera. 

 External antennae more or 

 less rudimentary and al- 

 ways inconspicuous. 



r 



4 Leucosina. 



5 Calappina. 



