
’s RIJKS MUSEUM VAN NATUURLIJKE HISTORIE — LEIDEN. 137 

as the lateral ones, sharply defined and separated by a deep groove; all 
the lobes bear, as de Man remarked (1895, p. 169), along their whole 
fore margin a transverse, rather deep groove. The front which is bent 
rectangularly to the postfrontal lobes, is slightly concave and projects at 
its free margin into two lateral projections, separated by a deep sinus, 
which is described by de Man (l.c.) as broad, not deep, but as no figure 
is provided by this author, the appreciation of this character remains 
subjective. The surface of the carapace is covered on the protogastric 
regions by a number of rounded tubercles, among which are scattered 
some larger ones; besides there are on the postfrontal lobes some groups 
of short, black hairs. The hepatic regions are provided with larger 
tubercles, the largest one of which is transversely elongated, immediately 
before a shallow groove, running transversely and parting from the in- 
cision between external orbital angle and epibranchial tooth. The external 
orbital angles are acute, directed forward, their outer margins are some- 
what convex, converging distally; the epibranchial tooth is obtuse, an- 
terior and lateral margins form a rectangular angle, and the latter are 
perfectly straight and parallel to each other. As de Man remarked, a 
second epibranchial tooth, though extremely minute, may be present or 
absent. According to this author the lateral margins of the carapace are 
nearly parallel, and the same character occurs in the older specimen 
from Borneo, but in the specimen from Balikpapan here figured the sides 
are somewhat diverging distally. 
The chelipeds are of equal size; the superior margin of the arm is 
armed with a subdistal rectangular projection, but no real tooth; the 
anterior margin is serrated and the distal half somewhat expanded and 
provided with some larger teeth. The carpus has at its inner margin a 
thin, lamellar expansion, serrulated at its distal half and ending in a 
sharp spine. The upper surface of the carpus and the outer one of the 
palm are covered with large, black, rounded tubercles; those on the palm 
are largest towards the upper margin, gradually becoming smaller and 
more acute towards the carpal joint and the middle of the outer surface ; 
at the inferior margin of the palm towards the base of the immobile 
finger and at the inferior margin of this finger, the tubercles are trans- 
formed gradually into acute spines directed forward. The most charac- 
teristic feature of the species consists in the remarkable flattened shape 
of the palm; looking from above, the outer surface is even slightly 
concave and rises into a well marked projection at the proximal end of 
this flattened region. This character is far more pronounced in the West- 
African Sesarma biittikofert de Man, in which the outer surface of the 
palm is perfectly smooth and flattened like a looking-glass, but is carried 
50 5 
