402 



Dr. ^Y. T. Caiman on 



VCQ.S presumably chelate in the lobster-like ancestors of the 

 crabs. Some of the objections to this view, however, are no 

 less obvious — e. g., (1) the resemblance is not to a gene- 

 ralized type of chela, but to the specific type of Cancer 

 pagurusi (2) in this very species a chelate form may be 

 assumed by the third maxUliped, a limb which is not nor- 

 mallv chelate in any decapod (Bateson, 'Materials for the 

 Study of Variation/ 1894, p. 149). 



2. Duplicity of Chela in Portunus puber (Linn.). 

 fFigs. 2 and 3.) 



The specimen is a male, measuring 68 mm. across the 

 carapace : it was found at Lvme Regis, and presented by 

 Mr. J. Curtis (B. M. Crust, reg. no. 1905. 9. 13. 1). The 



Abnormal cbeliped of Porttmus puber, inner aspect. Natural size, 



left chela is much larger than the right, measuring 49 mm. 

 as ao-ainst 35 mm. along the lower edge. On the inner side 

 of the left carpus, in the position occupied in a normal 

 cheliped by the carpal spine, is attached a second, smaller, 

 carpus, marked off from the first by a groove, which, however, 

 does not form a movable articulation. It would, perhaps, 

 be more correct to speak of this as the distal portion of a 

 carpus, since it is improbable that it repeats the region 

 proximal to its junction with the normal limb ; but this 

 cannot be determined with certainty. In form it resembles 

 closelv a normal carpus, except that the granulated ridges 

 and furrows of the upper surface are indistinctly marked. 

 It bears a large carpal spine of normal form, with three 

 small secondary teeth on its concave distal edge. As nearly 

 as can be judged^ the long axis of the secondary carpus forms 



