COUES ON A BREED OF SOLID-HOOFED PIGS. 297 



of the proximal phalanges. It is perfectly whole, or "solid", as seen 

 in the figure. In front, there is a slight, though evident, vertical line of 

 impression along the middle, indicating its composition from lateral 

 halves. Ou the sole of the hoof, there is a broad, angular elevation of 

 horny substance, apex forward, and sides running backward and out- 

 ward to the lateral borders of the hoof, the whole structure being 

 curiously like the frog of the horse's hoof. In fact, it is a frog, though 

 broad, flattened, and somewhat horseshoe-shaped, instead of being 

 narrow, deep, and acute, as in the actual frog ot the horse. This 

 arcuate thickening of the corneous substance occupies about the middle 

 •third of the whole plantar surface of the hoof. 



Viewing the apparent establishment of this pseudo-perissodactyle 

 structure in an artiodactyle, the question arises whether we have not, 

 under our eyes, au example of a way in which a solidungnlate may be 

 evolved from a pluridigitate stock — though of course the one case is by 

 enlargement of a single median digit and reduction of lateral digits, 

 while in the present instance a bone in the axis of the limb is produced 

 by failure of fission between lateral paired digits. Nothing is more cer- 

 tain than that the present solid-hoofed horse has come by direct descent, 

 with modification, from its several-toed ancestors of the Tertiary. In 

 the present case, we seem to have the initial steps of an actual trans- 

 formation which may in tiaie result in modifications to which ordinal 

 value may attach. It may be suggested that this modification is one 

 of progressive adaptation of the animals to their freely-ranging state 

 on the prairies of the country, just as the series of modifications which 

 the primitive horse's foot has undergone in adaptation to the making of 

 the most serviceable hoof for running on hard ground at the expense of 

 any other function. 



