0. C. Marsh — Recent Polydactyle Horses. 



345 



two united cuneiform bones. The lower extremity of this 

 metatarsal carried a single phalanx, with a posterior sesamoid 

 evidently formed of two bones. The main cannon bone 

 and its phalanges show no marked peculiarities except some 

 obliquity. The fourth digit is represented by a large splint 

 metatarsal, as shown in figure 4. The opposite hind foot 

 appears to be similar in all respects, except that the three 

 small cuneiform bones are separate, as shown in figure 9. 



Figure 8. — Right carpals and metacarpals of "Clique." 



Figure 9. — Right tarsals and metatarsals of same animal. One fourth natural size. 



a, astragalus; c, calcaneum; cb. cuboid; 1, 2, 3, 4, cuneiform bones ; I, lunar; 



m, magnum ; n, navicular ; p. pisiform ; s, scaphoid ; td, trapezoid ; tm. trapezium. 



In no case examined by the writer has there been conclusive 

 evidence of any extra digit except one of a true pentadactyle foot, 

 such as is now known in the ancestry of the horse. In every 

 specimen examined, where the carpal or tarsal series of bones 

 were preserved, and open to inspection, the extra digits were 

 supported in the usual manner. No instances of true digital 

 division were observed, although such cases might be expected. 

 It is noteworthy that none of the extra toes examined repre- 

 sents the fifth digit, although the reappearance of this rather 

 than the first might naturally be looked for. ]STo digit has 

 been noticed with more than three phalanges. 



A large majority of the polydactyle horses known to the 

 writer in this country, have been raised in the Southwest, or 

 from ancestry bred there, so that their connection with the 

 Mustangs or semi-wild stock of that region becomes more than 

 probable. It is well known that the tendency to reversion is 

 much stronger where animals run wild, and this fact must be 

 taken into consideration in discussing the present question, for 

 the late ancestors of the Mustang were certainly wild for at 

 least several hundred years. 



