1903.] FRESHWATER CRAB FROM UPPER GUINEA, 45 
the under margin; the latter is also slightly tubercular along 
its distal half. The three faces of the arm are quite smooth. 
The carpus is also nearly smooth above, though sparsely and 
rather finely punctate; the inner margin is armed with a rather 
small pointed spine in the middle and beneath it with a small 
acute tubercle. The larger chela (Pl. IX. fig. 5), measured 
horizontally, is a little longer than the length of the cephalothorax 
and the fingers are a little longer than the palm; the latter is 
just as long as high near the articulation of the fingers. The 
convex outer surface of the palm is quite smooth, though finely 
punctate, similar to the upper margin, but the lower edge of the 
palm is obsoletely tubercular. The fingers are somewhat compressed, 
especially the immobile one. The immobile finger is rather high 
at the base; its flattened outer surface appears minutely and 
densely granular under an ordinary Jens, and one observes on it 
three longitudinal rows of impressed points running to the tip of 
the finger, the middle one of which is situated a little closer to 
the lower margin of the finger than to the upper, and looks 
like a very shallow furrow. The 15 or 16 teeth are small, two 
or three are somewhat larger than the others, and one in the 
middle of the finger is the largest of all. The fingers leave a 
narrow interspace between them when closed, the pointed tips 
being only in contact and crossing one another. The dactylus is 
somewhat arenate and tapers rather slowly to the tip; both on 
the outer and inner surfaces and on its upper edge this finger 
appears minutely granular under a lens, and one observes on it 
several rows of small shallow puncta. The teeth agree in size and 
in number with those of the index, three or four being somewhat 
larger than the others. The little convex inner surface of the 
palm is quite smooth, 
The left chelipede is somewhat smaller, the hand being 41 mm. 
long; it fully agrees with the right one, but the fingers are in 
contact and the rows of puncta are a little more distinct, 
In the young male from Liberia the fingers are in contact in 
both chele, the upper margin of the palm appears distinctly 
granulate under a lens, and the longitudinal furrows on the 
fingers are already visible to the naked eye. 
In the young female from Liberia the right chelipede is a little 
larger than the left, the fingers are in contact, and the furrows 
on the index, as also the rows of puncta on the mobile finger, 
ave distinctly visible to the naked eye. The upper margin of the 
palm of the left hand appears finely granular. 
In the aged female from the River Prah the left chelipede is 
much larger than the right; the hand, indeed, is 45 mm, long, 
just as long as the cephalothorax, and 203 mm. high, but the 
right chela (Pl. IX. fig. 6) is only 31 mm. long and 13 mm. high, 
In both the fingers are in contact throughout their whole length 
and the pointed tips cross one another; the strongly compressed 
and much flattened immobile finger is not furrowed, though the 
