300 Dr. Strahl on the Limits of the Brachyura. 
I propose to name R. truncata, because the frontal margin is 
not distinctly toothed, but almost entirely smooth as in R, vi- 
nosa, M.-E. R. truncata is further distinguished from R. annu- 
lipes, and also from R. vinosa, by the lower margin of the orbit 
bearing four small teeth, and from R. annulipes, M.-E., by 
the want of the horizontal ridge upon the teeth of the lateral 
margin, by which the latter is specifically distinguished. __ 
The genus Riippellia consequently includes four well-marked 
species. The Cancer Calypso, Herbst, which Milne-Edwards 
supposed might belong to Riippellia, belongs to the genus Pilum- 
noides, Dana. Riippellia is most nearly allied to Ozius, Leach ; 
for, besides that, as Dana has already pointed out, the spatium 
prelabiale is distinctly divided on each side by a longitudinal 
seam, and the efferent canal of the branchial canal thus bounded, 
corresponding to the anterior margin of the third joint of the 
external maxillipeds, exhibits a round emargination, the form of 
the first joint of the external antenne agrees in Ozius and 
Riippellia ; this joint, in its course from behind forwards, is bent 
in the form of a knee from within outwards. The agreement in 
external structure is so great in the two genera that they might 
conveniently be united in a single one, but for the presence of a 
distinction which refers each of these genera to a particular divi- 
sion. Thus, in Riippellia the pterygostomium and forehead come 
so close together that the orbit is thereby completely closed in- 
ternally, as in Hriphia and Trapezia; whilst these parts in Ozius 
leave a cleft between them, in which, as in the allied genera 
Galene, Pilumnus, &c., the moveable portions of the external 
antenne conceal themselves. 
Dana’s Ozine enable the Eriphine to be approximated to the 
Xanthine and Chlorodine, in so far as in the Ozine, Xanthine, and 
Chlorodine, and likewise in the Portunide, the pterygostomium 
never closely approaches the forehead, and completely closes the 
orbit internally, but a wider or narrower cleft always remains 
here ; if the orbit be nevertheless closed internally, this is always 
effected by the first joint of the external antenna, which is then 
of large size, as in Melissa (Euxanthus, Dana), Etisus, Thala- 
mita. The Eriphine might probably be arranged next to the 
Oxyrhyncha, which I formerly limited more accurately ‘%s Bra- 
chyura perfusa; in the latter the amalgamation of the pterygo- 
stomium with the first joint of the external antenna and with the 
epistomium effects the complete closure of the orbit, and the se- 
cond joint of the antenna is always inserted at the summit and 
in front of the orbit. 
As I have already indicated, the group of Brachyura incuneata 
established by me includes by far the greater part of the Bra- 
chyura; and decided differences of organization call for a further 
