The Cubital Coverts of the Euronithce. 325 



But althougli that particular feature had now been noticed 

 repeatedly in the course of dissection, it does not seem to 

 have occurred to any one that any external and easily- 

 examined evidence of the presence or the absence of the fifth 

 cubital remex could be traced. Yet so it is. In the orioinal 

 paper dealing with the cubital coverts of birds I laid great 

 stress upon the fact that all the Euornith?e might be 

 divided into two sections according to whether they did, or 

 did not, possess what I then termed the "Supplementary 

 row of Median Coverts, or Upper Wing Coverts." I pointed 

 out that the possession of the feature referred to coincided 

 with that of several structural characteristics of considerable 

 importance {op. cit., p. 191). Since Mr Wray's paper has 

 been published it occurred to me that there might be some 

 connection between the curious break in the arranaement of 

 the wing coverts, and the presence or the absence of the 

 fifth cubital remex. This has proved to be correct in so 

 many cases that I shall assume it to be true for all. An 

 examination of a large number of aquincubital wings showed 

 clearly that, from the point where the fifth cubital remex is 

 missing, up to the margin of the wing above, there is a 

 marked disturbance of position of all the coverts. In the 

 case of the homalogonatous ^ birds with the desmognathous ^ 

 type of palate, the displacement takes the form of a down- 

 throw on the side next the outer maroin of the wingf. The 

 wing coverts, in fact, are what geologists would describe as 

 "faulted," and the course of the "fault" can be distinctly 

 traced by the disturbance of the coverts it causes right across 

 the wing. The Major coverts are generally displaced less 

 than the Medials, but there can be no doubt about the fact. 

 (See the figure of the Duck (Fig. 14), the Pigeon (Fig. 17), and 

 the Tern (Fig. 20) as illustrations of this displacement.) In 

 certain birds, to be noticed in more detail presently, the 

 line of displacement coincides with a change of direction of 

 overlap, usually from proximal to distal. This external 

 mark of aquincubitalism was made known for the first time 

 on the evening when the second instalment of this paper 



1 See Garrod, Proc. Zool. Soc, 1874, Xo. viii., p. 116. 

 ^ See Huxley, Proc. Zool. Soc, 18(37, No. xxvii., p. 450. 



