PKENTISS : POLYDACTYLISM IN MAN AND DOMESTIC ANIMALS. 265 



wedge-shaped and divided into two facets of nearly equal size, the radial 

 for articulation with metacarpal ii, the ulnar for the large process of 

 metacarpal iir. The os magnum articulates distally with the third meta- 

 carpal only ; the unciform has distally a small facet for the ulnar pro- 

 cess of metacarpal iii, a large one for metacarpal iv, and a small facet 

 laterally placed for metacarpal v. 



lun. 



mag. 



III. 



Fig. G. — Left manus of Ancodus brachyrhynchus, showing carpals and metacarpals. 

 i-v, first to fifth metacarpals; lun., hmar; os mng., os magiuim; scph., scaphoid; trz., 

 trapezium; irztZ., trapezoid; ««., unciform. § natural size. (After Scott.) 



If we compare the carpus and metacarpus of the pig with those of 

 fossil swine (Palaeochoerus and Hyopotamus or Ancodus) figured hy 

 Kowalevsky ('73) and Scott ('95), we find some remarkable differences. 



In Hyopotamus (Ancodus of Kowalevsky) the trapezium (Fig G.) is 

 nearly as large as the trapezoid, and articulates superiorly with the 

 scaphoid, iuferiorly with the metacarpal of digit i. The trapezoid has 



