THE FOSSIL FOOTMARKS OF THE UNITED STATES. 239 



tiful specimens of this species, with the small fore foot as distinct 

 as the hind one. One of these specimens is sketched on Plate 22, 

 fig. 8, reduced three times. It was, however, only on a fine speci- 

 men in Professor Shepard's cabinet that I have discovered a fifth 

 toe on the fore foot, too distinct to be doubted. I am still 

 somewhat suspicious that this and the preceding species (M. recta) 

 may turn out to be the same ; although the latter is a good deal 

 larger, the toes much straighter (hence the specific name), and, if 

 I have not mistaken the character of the fore foot, this also differs 

 a good deal, having a large heel. Both these species differ from 

 the M. rlujnchosauroidea, by having a quite different heel, and four 

 or five toes, instead of three, on the fore foot. 



Plate 22, fig. 10, is a sketch, of the natural size, of two rows 

 of tracks on a slab in Mr. Marsh's collection. The fore tracks 

 are much better developed than the hind ones. They appear to 

 be the smallest of all tracks yet discovered. If they are the M. 

 divaricans, they must have been made by the young of that species. 



Gems XIX. XIPHOPEZA. 



Tetradactylous : three toes directed forward ; the fourth being a 

 prolongation backward of the outer toe. Heel stout, expanding 

 posteriorly. Hind and fore feet unequal, resembling three swords, 

 or daggers, in a complex sheath. 



Species 1. Xiphopeza triplex. (PI. XV. Fig. 8.) 



Specimens in the cabinet of Mr. Dexter Marsh. 



Hind feet. — Three toes directed forward. Divarication of the 

 outer toes, 80° to 90° ; of the inner and middle, 40° ; of the mid- 

 dle and outer, 50° ; of the middle and hind, 130° ; of the hind 

 and outer, 180°. Length of the inner forward toe, 0.8 inch; of 



