MUSEUM OF COMPARATIVE ZOOLOGY. 259 
its toothed margin. One of these (b) seems to be developed in order to 
recover the prehensile power which was lost by the distortion of the 
dactylus. "The other (c) is broken off near its tip, but corresponds to 
the process c described in the next figure. 
There is another dactylus in the collection quite similar to this. 
Plate I. Fig. 8 (right chela). — This deformity belongs to the same 
category as the one represented by the last figure. The dactylus (a) is 
curved strongly away from the index, and lengthened. At d is the scar 
resulting from the wound that probably caused the curvature of the dac- 
tylus. An outgrowth (b) provided with teeth, and meeting the thumb 
when the claw is closed, replaces functionally the distorted extremity of 
the dactylus. In addition to this a second process (c) projects at a 
right angle with the deflected part of the dactylus. This process pre- 
sents a line of teeth opposite to those on a. My reason for considering 
a rather than 6 to be the end of the original dactylus, and 6 and e to be 
secondary outgrowths, comes from the arrangement of the punctures 
and the striso on the cuticle of these parts, which seem clearly to show 
that 6 and c are the newer portions. 
Plate T. Fig. 9 (right chela). — The index here is split into two parts. 
The outer (a) is toothed on its inner border. The inner (0, c) is toothed 
on both margins, and shows a tendency to divide at the end. ‘The lines 
on the cuticle show that a is the original index, and 5, c, a secondary 
process developed from it. The dactylus does not meet the index when 
closed. 
Plate. I. Pig. 10 (right chela). — The dactylus is abnormally short 
and curved, and its proximal half produced into a large roundish plate, 
toothed on its margin, only the basal part of which closes against the 
index. 
Plate I. Fig. 11 (left chela). — A large triangular crest, directed out- 
ward and forward from the middle of the outer margin of the penulti- 
mate segment. This erest-like process has a strong curve downward. 
There are several claws similar to this in the collection. 
Plate 1. Fig. 12 (right chela). — The inner border of the hand is dis- 
torted by a wound (d) which has resulted in the outgrowth of a simple, 
blunt, movably-jointed segment (a^), which evidently represents an abor- 
tive supernumerary dactylus. On its upper sido (the figure shows the 
lower surface), near the articulation with the hand, is the small spine 
characteristic of the normal dactylus. The abnormal finger moves in a 
plane at right angles to the plane of motion of the normal dactylus. 
There is another specimen in the collection similar to this, —a left 
