106 REPORT OF COMMISSIONERS OF INLAND FISHERIES. 



chela, but also because their morphological surfaces are structurally 

 continuous throughout the limb. In regard to position, the index 

 and dactyl are thrown horizontally outward at an angle of about 

 45 degrees from its normal relations to the chelse. 



At the inner or morphologically dorsal side of the second segment 

 (d) there is a broad expansion of the propodite, so that this segment 

 appears practically double, and is almost twice its ordinary size. 

 Upon the periphery of this extra propodite structure are set two 

 extra segments (D'R' and D'L'). They are practically equal in 

 size, and each of these segments forms a true joint with the propodite. 

 The tip of one of these extra parts (D'L') has been broken off, and 

 a small area (a) is also gone from its toothed border. The general 

 form and relation of these two extra segments clearly show that 

 they are both dactyls; the character of the dentition, together with 

 scattered tufts of tactile hair, also brings these two dactyls under 

 the "nipper" type of claws. 



Between these t'^\^ extra dactyls there projects from the propodite 

 a small spur F (R+L). A closer examination of this process showed 

 that it was slightly bifurcated at its tip; and what is still more 

 significant, that down two of its opposite sides there is a more or 

 less regular row of rudimentary teeth. These two rows of teeth lie 

 in a common plane with the two dactyls; consequently, the rela- 

 tions are such that the toothed borders of the flexed dactyls play 

 upon the rudimentary teeth of this process, in a manner very similar 

 to that of a normal dactyl and index. The evidence, then, seems 

 to justify the conclusion that this extra structure is morphologically 

 really a double index. And, therefore, that this double index, to- 

 gether with the two dactyls, represents two extra claws. 



In this abnormal chela, then, we have three claws. The extra 

 pair is at about right angles with the normal claw, and the three 

 claws also lie practically in a common plane. The significance of 

 the fact that D and D'R', D'R' and D'L', are respectively minor 

 images of each other will be taken up later under the head of " Dis- 

 cussion. " 



