i8 95 . THE STRUCTURE OF ARCH&OPTERYX. 121 



And again, the digits I, II, III of Archceoptevyx (which the large 

 size and perfectly ossified bones show to be an adult, as also do the 

 well- developed feathers) are, by virtue of their very great slenderness 

 and narrowness at the joints, incapable of resisting a great torsional 

 stress. Unless those feathers exert a great torsional stress on the 

 bones supporting them they are useless. I have shown they were 

 not useless. Therefore they exerted a great torsional stress, and 

 therefore they were supported by bones not yet seen in the Berlin 

 specimen, although those of the left wing are seen in the London 

 specimen. It follows, therefore, that the first three digits were used 

 for climbing, and that one or more others were present to support the 

 feathers. That two were needed I hope to prove in another place. It 

 would unduly increase the bulk of the present article to prove it here. 

 It is unnecessary, in view of the fact that anybody may see the two 

 metacarpals for himself in the Museum in Cromwell Road. 



(3.) The third proof is incomplete. It shows only that the digits 

 I, II, and III did not support the feathers, and that, therefore, some- 

 thing else must have existed to do so. Its simplicity is unsurpassed. 

 It will appeal even to those who ignore both the principles of mechanics 

 and the action of Natural Selection. The figure 10 is placed on the 

 surface of the right wing in Plate I. In this region the dorsal surface 

 of the wing is convex. A rule or "straight-edge" placed on the 

 wing across this point, parallel to the ulna and resting upon the 

 first and second digits, touches the wing along the whole of its length 

 from number 10 backwards. In front of this the feather-surface 

 curves downwards, so as to be perhaps 2 mm. below the edge of the 

 rule near the digits. The loivev surface of the. metacarpal and of the 

 first and second phalanges of the second digit lies fully 1 mm. above 

 that feather-clad surface. The bones of the third digit are closely 

 pressed down upon, but not sunk below, that surface. Therefore those 

 digits did not lie in but upon the feathered wing when that animal 

 finally sank dead upon the mud in which it has been preserved. 

 Therefore, further, other bones (or bone) were present to support those 

 feathers. No argument from the embryology of Opistlwcomus or 

 anything else will shake that conclusion. Whatever argument be 

 urged in future against this view, all that can be shown thereby is the 

 fallacy of the reasoning — but I will return to this in the sequel. 



I must here correct an error made in my previous article. The 

 supposed " shadow" (see 12 on the plate accompanying this article) 

 which I referred to is not a shadow at all, but a yellow stain on the slab. 



The pelvis is seen in the London specimen only, and in this speci- 

 men nothing is to be learnt from the left innominate, while even the right 

 one is imperfect (Fig. 2, a). This innominate appears to have been 

 about 50 mm. long. The acetabulum is perforate. I believe there is 

 no anti-trochanter, though in absence of the specimen I would not 

 make the statement definite. It is a characteristically avian pelvis so 

 far as concerns the length of the ilium and its prolongation to about 



K 



