46 DR. J. G. DE MAN ON A NEW [Jan. 26, 
rows of puncta are still visible. The fingers are but little longer 
than the palm, and the latter is on its outer surface and on its 
upper margin smooth, sparsely punctate. The fingers of the 
smaller chela, however, are once and a half as long as the palm 
(Pl. TX. fig: 6). 
The female type-specimen of P. africanwm compared with the 
female from Liberia, which is about the same size, shows the 
following differences :—The anterior legs (Pl. IX. fig. 9) are equal, 
as regards their shape and size. The transverse rugosities on 
the upper margin of the arm are more distinctly granular, and 
the anterior and lower margins are also more distinctly tuber- 
culated ; the conical spine on the anterior surface, near the articu- 
lation of the wrist, is more pointed, and several small tubercles 
are seen between it and the anterior margin of the arm, that are 
wanting in P. latidactylwm. The upper surface of the carpus is 
slightly granular at the base of the spine on the inner margin, 
and one observes, moreover, everywhere fine impressed lines and 
points; the spine is somewhat larger than in P. latidactylum, 
and instead of a small tubercle, there is beneath it a smaller, 
pointed spine. The hands (Pl. IX. fig. 9) have a quite different 
form. The fingers, almost in contact, are distinctly somewhat longer 
than the palm, and the latter is distinctly less high than long. 'The 
upper margin of the palm is covered with depressed granules, 
and the puncta on the convex outer surface are partly arranged 
in longitudinal rows. The fingers are not compressed, slender, 
nor curved, except at the pointed tips which cross one another. 
The immobile finger is much lower at its base than in the 
other species, and its convex outer surface is distinctly furrowed ; 
of the three furrows visible to the naked eye, the middle one is 
deeper than the others. This finger is armed with 25 or 26 small 
teeth, some of them on the proximal half are somewhat larger 
than the others. Finally, the dactylus tapers regularly to the tip 
and is also longitudinally furrowed by rows of impressed points ; 
the teeth agree with those of the index. The fingers are almost 
smooth. 
The ambulatory legs, the measurements of which are given 
on p. 47, apparently agree with those of P. latidactylum, but the 
meropodites are more granular along and near their upper edges. 
Potamon aubryt AH. M.-E., from the Gaboon, P. pelii Herklots, 
from the Gold Coast, and P. flowert de M., from the Soudan, are 
different species (vide de Man, Proc. Zool. Soc. Lond. 1901, vol. i. 
p- 94), being at first sight distinguished by the upper surface of 
their cephalothorax being very convex from behind forwards, 
smooth and shining, by the different form of the fingers, of the 
abdomen, &e. The young male of Potamon pelii described J. e. 
p. 99, I have re-examined for the purposes of this memoir, 
