1926] Schmitt, Crustaceans Collected by the Congo Expedition 47 
high; in the typical arrosor it is more than twice (nearly two and one- 
fourth times) as long as high at the middle of its length; moreover in 
the latter the outer face of this joint is not at all grooved, though the 
meeting of the striz running down from the upper half of the outer surface 
with those running up from the lower half, along the median longitudinal 
line, gives the optical illusion that the surface is grooved along that line. 
In reality, the outer face of the propodus is quite bowed out, rather 
evenly convex and more ridged than not along its median longitudinal 
axis. Along this line the propodus of D. pectinatus is distinctly depressed 
or grooved, as is also the dactyl; in arrosor this joint shows but little 
more than a suggestion of a groove as compared to the rather widely and 
deeply troughed dactyl of D. pectinatus. 
The striz on the outer surface of the second ambulatory leg in D. 
arrosor are but minutely, almost imperceptibly roughened at the bases 
of the hairs inserted along the anterior margins of the striz, while in D. 
pectinatus they are noticeably roughened and rugulose over their surface, 
the anterior margins of the striz plainly spinous-tuberculate. This differ- 
ence in armature is even more pronounced in the striations of the hands, 
not only being very evident to the eye, but also to the touch when run- 
ning the finger over them. In fact, the strongly spined chela of D. 
pectinatus readily differentiates it from the typical form with which it 
has long been associated. In D. arrosor approximately the outer two- 
thirds of the upper surface of either hand is unarmed, except for the char- 
acteristic transverse strie or rug; the inner remaining third or less of 
the upper surface has three or four not-too-distinct rows of spinous 
tubercles. In D. arrosor, except in the case of the more continuous row 
of spines forming the inner margin of the palm, these spines occur, one or 
two (or rarely three) to each of the longer, less interrupted rugee. In D. 
pectinatus almost the entire ruge on the hands are crowded with spin- 
ous tubercles, each and every one; moreover, these tubercles become 
increasingly prominent as one goes across the upper face of the palm from 
the outer margin toward the inner one, where they are two and three 
times as large as the spines in specimens of D. arrosor of about the same 
size. 
The proportions and the shape of the larger chela differ also in the 
two species. The palm is more squat and less parallel-sided in D. pec- 
tinatus, the greatest width just before the base of the hand is contained 
about one and one-third times in its length from the outer articulation 
with the wrist to the tip of the immovable finger; in D. arrosor the great- 
est width of the palm is contained twice in the corresponding longitudinal 
