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176 DR. J. G. DE MAN ON THE PODOPHTHALMOUS 
I was inclined at first to regard this species as a mere local variety 
of de Haan’s Sesarma bidens, but after a more careful examina- 
tion I consider it to be a distinct species. Sesarma Haswelli, 
however, is most closely allied to Sesarma bidens, de Haan. As 
regards the form and structure of the cephalothorax, both species 
closely resemble one another, not only with respect to the 
upper surface and the form of the front, but also with respect 
to the form of the joints of the male abdomen. The ambulatory 
legs also completely resemble those of Sesarma bidens, as regards 
the comparative length and breadth of the joints; and their 
coloration is the same in both species. S. Haswelli only differs 
from S. bidens by the number and by the form of the tubercles 
of the upper margin of the mobile finger. | 
The mobile finger is a little less arcuate at its base than that 
of Sesarma bidens, being more straight, and it is covered in the 
right hand, which in our larger specimen is a little larger than 
the left, with a longitudinal row of 18-19 tubercles, whereas in 
the left there are only 16 tubercles. In Sesarma bidens only 
13 tubercles are constantly found on the upper margin of the 
mobile finger. These tubercles have a different appearance in 
the two species, extremely difficult to describe. 
In Sesarma guttata from the shores of Zanzibar, the mobile 
finger is covered above with 12-13 tubercles; in this species 
these tubercles are ovoid, rather prominent, and their longer 
axis is transverse, making a right angle with the longitudinal 
axis of the finger. These symmetrical tubercles completely 
resemble some species of Chiton, for they present a smooth 
ridge in the middle, which runs in the longer axis of the tubercle - 
and which is transversely sulcate. 
In Sesarma bidens the tubercles are similar to those of S. gut- 
tata, but they are lower and much less prominent. In Sesarma 
Haswelli, however, the tubercles are less distinctly Chiton-like ; 
they are more depressed above and are scalariform, each tubercle 
being nearly vertically deflexed at its distal margin towards 
the ¥ent; they are transverse, as in all species of this section 
of the genus, the longer axis being perpendicular to the axis of 
the finger. 
In all other characters the hands are similar to those 
of S. bidens. The outer surface of the immobile finger is 
somewhat flattened, or slightly concave, presenting a slight 
longitudinal, ridge-like elevation below, parallel to the under 
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