240 Mr. R. I. Pocock on 



character may be taken exception to. Size by itself is of 

 course valueless ; the colour of the legs, as shown by the 

 Museum series, varies from very dark brown to clear paleyellow 

 — thus in specimen J they are very deep brown, in A light 

 brown, in F dark yellow, in M pale yellow ; the fifth caudal 

 segment is shorter than the cephalothorax in females, as long 

 in males of a certain age, and longer in large males ; and the 

 vesicle, as stated above, is wider than the fifth caudal seg- 

 ment in adults and of the same width in young forms ; the 

 groove on the upper surface of the vesicle varies from being 

 invisible to clearly pronounced ; the sculpturing of the hand 

 is also a matter of individual variation. 



The only character that seems of importance is the width 

 of the hand, for in lucidipes it is stated that the hand is wider 

 than it is long. Now, a glance at our table of measurements 

 shows that, although subject to variation, the length of the 

 hand is always greater than the width ; so that when, in 

 addition to the statement about lucidipes, it is noticed that 

 Mons. Simon asserts that in Swammerdami the width of the 

 hand is as great as the length, the conclusion seems almost 

 inevitable that his measurements have been taken along 

 different lines from those in the table. In the table the 

 greatest width is taken along a line at right angles to the 

 axis of the brachium, and the greatest length from a point on 

 the anterior (inner) surface at the base of the dactylar pro- 

 longation to the extremity of the dilatation of the hand. 

 And this measurement of the length always exceeds that of 

 the width. If, however, the width be taken from the point 

 of articulation of the movable dactylus to the extremity of the 

 dilatation, it will be found to be as great or greater than the 

 length. 



That this explanation is the true one is rendered practically 

 certain by the fact that in the figure of the type of Sc. Swam- 

 merdami the form of the hand is the same as in the specimens 

 in the Museum collection, and that when measured as these 

 have been measured the length is always greater than the 

 width. 



Sufficient grounds have now, I think, been found in each 

 case to justify the conclusion respecting the specific identity 

 of the forms that have received the above names. 



