274 



bulletin: museum of compaeative zoology. 



has become enlarged to correspond with the increased size of its digit 

 (ii) ; it articulates chiefly with metacarpal ii, its facet for ni bein"- 

 small. The radial process of metacarpal iii is considerably reduced. 

 In another case (Plate 7, Fig. 15) the trapezium was fused to the 

 proximal end of metacarpal i. 



In Figure 16 (Plate 8) is shown a raanus which exhibits an extremely 

 interesting structure. The extra digit is identical in its structure with 

 that of the manus figured in Plate 6, but the second digit is very 

 strongly developed, and is in fact more massive than either iii or iv. 



trzfl. OS mag. 



Fig. N. — Anterior view of left polydactj-le manus of the pig, showing lower row of 

 carpals and metacarpals, i-v, metacarpals; os mag., ps magnum; trz., trapezium; trzd,, 

 trapezoid ; un., unciform. | natural size. 



Its hoof is large, convex on its radial, and flat on its ulnar surface ; it is 

 entirely independent of the hoof of digit in. The third plialanx of 

 digit II is al.so convex on its radial side; that of digit iii is indiff"erent, 

 and its hoof is flat on eitlier side. The other digits are apparently 

 normal. Of the carpals, the trapezium (Fig. N, trz.) is large and artic- 

 ulates with tiie scaphoid, trapezoid, and metacarpal i. The trapezoid 

 (trzd.) is nearly as large as the os magnum (os mag.), and its single 

 distal facet articulates with only metacarpal ii. 



Of the metacarpals, i is small but v>ell formed ; ii is larger than in 

 at its distal end and shows evidence there of pathological hypertrophy. 



