1888.J 



Wings of existing Carinate Birds. 



323 



these parts in every main group of the Class. Normally, both the 

 existing Carinatse and Ratitae, and such extinct forms as have been 

 "worked out — Archceopteryx, Hesperomis, Iohthyornis — show that the 

 primary form of the bird's wing is simply tri-digitate. In this I agree 

 with Baur, who has helped me greatly in this matter, both by his 

 valuable papers and also by personal discussion with me. 



The normal " manus "of a carinate bird contains two per- 

 manently distinct carpals : three carpals that lose their independence 

 by ankylosis with the metacarpals, and three digital rays extending 

 from the three fused metacarpals. 



In some birds, e.g., the Passerinse, the pollex of the first digit has 

 only one phalanx attached to its short metacarpal, the second only two, 

 and the third only one, phalanx. In others, Plovers, Gulls, Cormorants, 

 &c, an additional or ungual phalanx is found on the first and second 

 digit; and in some birds, e.g., Numenius, during their embryonic state, 

 a small nucleus arm is seen on the end of the aborted phalanx of the 

 third digit. „ 



In my as yet unpublished paper I have mentioned a sub-distinct 

 tract of very solid fibro-cartilage, which evidently corresponds with 

 what has been called " prae-pollex " by Kehrer and others.* , 



I am satisfied, now, that this very notable part is the remnant of 

 the skeleton of the spur, so remarkably developed in the Palamedidae, 

 certain Geese, Plovers, and Jacanas. 



This part therefore need not interfere with the consideration of the 

 true secondary digital parts. 



Among the last communications received by me from Dr. Baur, 

 I find in print what I had already learned from him orally. 



In some " General Notes " published in the 'American Naturalist,' 

 September, 1887, p. 839, I find the following paragraph : " The 

 oldest Ichthyopterygia had few phalanges and not more than five 

 digits ; [the] radius and ulna were longer than broad, and separated by 

 a space. Later, through the adaptation to the water, more phalanges 

 were developed, more digits appeared, mostly by division of the 

 former, or by new formation on the ulnar side. I have never found a 

 new digit developed on the radial side." 



These are most important facts, some of which, namely, the bifur- 

 cation of the digital rays, I had received some light upon, before, both 

 from Dr. Gadow and from Professor D'Arcy W. Thompson. t 



I find that the carpus, metacarpus, and digital rays are all apt to 

 increase in number beyond what is normal. 



* " Beitrage zur Kentniss des Carpus und Tarsus der Amphibien, Keptilien, und 

 Sauger," 'Berichte der Naturforsehenden Gresellsohaft zu Freiburg i. B.,' vol. 1, 

 188(3 (Heft 4 and Taf. 4). 



f See his paper on the bind limb of Ichthyosaurus, &c., ' Journ. Anat. Phrsiol.,' 

 vol. 20, 188G, pp. 532-535. 



