ON THE BRACHYUROUS DECAPODS OF THE CAPE. 
65 
Fam. GRAPSIDiE, M. E. 
Sub-genus? Gnathochasmus, M‘L. 
Cephalothorax sub-quadrate, with the back convex, and entire sides which are arched towards 
the eyes; the clypeus between the eyes is plane, entire, truncated and deflexed. 
Exterior Antennae produced as far as the middle between the eyes, and having the first joint 
transverse. 
External Pedipalpi very distant from each other; with the second joint very oblique at the 
base, at the point sinuated, and of the same length as the third joint, which is concave in 
the middle, and has a bearded crest continuous along its inner edge as far as the outer 
part of the base of the second joint. 
Feet; first pair with thick and equal chelae. 
Abdomen in both sexes has seven segments. 
10. Dehaan has noticed the affinity between the two groupes, which he names Chasmagnatlius 
and Pachysoma. By them he passes from the family Ocypodidce to the family Grapsidae. 
The sub-genus or sub-section which I have j ust characterized under the name of Gnathochasmus 
comes exactly between Chasmagnatlius and Pachysoma. It agrees with both in the remark- 
able elevated crest, which stretches down obliquely from the inner angle of the third joint of 
the external pedipalp to the outer angle of the base of its second joint. It has the thorax with 
arched sides, like those of Chasmagnathus ; but then these sides are entire, like those of 
Pachysoma. I may here observe, that Dehaan’s name Pachysoma ought to be changed, as it 
was assigned, long ago, by Mr. Kirby, to a division of the genus Scaraboeus. See Horae 
Entomologicae, part 2, p. 607. 
Sp. 21. ( ) Gnathochasmus barbatus, n. s. 
Descr. Gnathochasmus testa loevi, utrinque ad oculos deflexa regionibus sub-distinctis, lateribus 
clypeoque marginatis integris ; manibus he vibus glaberrimis crassis chelis sub-eoncoloribus 
latis convexis, pedibus lae vibus sub-compressis nigro-punctatis tarsis sulcatis. 
Note. This crab is about an inch and a quarter long. 
Sub-genus. Sesarma, Say. 
Sp. 22. ( ) Sesarma reticulata, Say. 
Grapsus cinereus, Bose. Hist. Nat. des Crust, vol. i. p. 204. tab. 6. fig. 1. 
Sesarma reticulata. Say, Trans. Acad. Phil. vol. i. p. 73. tab. 4. fig. 5. 
Note. It is singular that I can find no good character whereby to separate this Cape crab from 
the American species described by Bose and Say. The latter, however, I only know from descrip- 
tion. It is six lines long, whereas the Cape crab is more than an inch. Both are distinguished 
from the Sesarma quadrata by their epistome being covered with granulations, so as to appear 
finely reticulated. I dare say if we could compare the two crabs together we should be able 
to discover a specific difference. The Cape crab has not the slightest vestige of granulation on 
the shell of the cephalothorax. I have found in Cuba the species of Sesarma to live generally 
under stones on the banks of the muddy mouths of rivers. Say’s name, Sesarma, is adopted 
K 
