CHAPTER IV. 



THE FAUNA OF THE EQUUS BEDS. 



The Equus beds form the superficial formation of the country at vari- 

 ous points on the Staked Plains and about its eastern escarpment. They 

 are always to be distinguished by the presence of Elephas primigenius 

 when other forms less easily preserved are not recognized. Mastodon is 

 always absent from Texas localities so far as yet observed, as in Oregon. 

 The terranes are more generally sandy than are those of either the Blanco 

 or Loup Fork epochs. In passing north from Big Springs, we first 

 definitely identified the Equus beds on Wild Horse creek, a tributary of 

 the Colorado, where they rested immediately on the Trias. Mr. Cum- 

 mins discovered a tract of the same on Rock creek, a tributary of the 

 Prairie Dog head of the Red river, on the Tule canyon, and from this 

 locality most of the specimens described in the following pages were de- 

 rived. The identification of species is interesting as showing the com- 

 plete difference which exists between this fauna and that of the Blanco 

 epoch. 



TESTUDINATA. 



TESTUDO, Linn. 



As no determination of tortoises has yet been made from undoubted 

 Equus beds, it is of interest that two species of terrestrial habits were 

 obtained by Mr. Cummins. 



TESTUDO LATICAUDATA, CopC. 



Sp. nov. Plate XXII, Figure 1. 



This tortoise is represented by a nearly entire left epiplastral bone and 

 a greater part of the right xiphiplastral. As these pieces present the 

 characters which define species of Testudo most readily, I can describe 

 the present form and compare it with its congeners, in spite of the absence 

 of other parts of the skeleton. 



The borders of both the elements in question are robust, and the lip 

 of the epiplastral is quite large. The mesoplastron is quite thick, but 

 the middle parts of the xiphiplastron are rather thin. The hyoplastral 

 sends a strong gamphosis into the epiplastral within the border, and the 



