GILMORE: the fossil turtles of the UINTA FORMATION 



109 



present specimen is therefore worthy of brief description. The nuchal scute is 

 small, having a length of 12 mm., and a transverse diameter of 17 mm. The 

 median part of the anterior border projects shghtly beyond the general contour of 

 the shell. The nuchal is flanked on either side by small rectangular marginals. 

 The arrangement and proportions of the scutes in front of the first vertebral are 

 very similar to those of Baena antiqua Lambe. 



This specimen shows many of the sutures between the costals, but on the 

 median dorsal surface their complete coalescence renders it impossible to differ- 

 entiate the neurals. There are no supernumerary costal scutes on either side of the 

 first vertebral such as found in many species of this genus and occasionally in 

 individuals pertaining to the present species. 



The plastron agrees almost exactly with the type in size and proportions, and 

 especially in the sculpture of the surface and the course of the various sulci. The 

 accompanying table gives a comprehensive comparison of the principal measure- 

 ments of the plastra. 



Comparative Measueements of Plastra. 



Width of bridge 



Length of anterior lobe . 

 Width of anterior lobe. . 

 Width of posterior lobe . 



No. 2356. 



145 



82 



108 



96 



Type of B. arenosa. 



140 



77 



107 



98 



Type ofB. affinis. 



125 



77 

 104 

 114 



The discovery of the present specimen in the Uinta formation of Utah in- 

 creases somewhat the known geographical as well as the geological range of Baena 

 arenosa. The type of the species is from the Bridger deposits at the junction of 

 the Big Sandy and Green rivers in southeastern Wyoming. Hay^ has identified 

 this species from the Washakie, the uppermost division of the Bridger. The type 

 of B. affinis is from level B, of the Bridger, which represents the middle of that 

 formation. Both Cope and Hay have identified specimens from the Wasatch of 

 New Mexico as pertaining to this species, these being the most ancient known at 

 the present time. With a geological range beginning in the Wasatch and ending 

 in the middle of the Uinta, Baena arenosa enjoys the distinction of having the widest 

 geological distribution of any species of the genus. 



2. Baena emiliae Hay. 



Baena emilice Hay, 0. P., Fossil Turtles of North America, 1908, pp. 80-81, PI. 

 XX, fig. 1 ; text-figs. 67, 68. 

 Six specimens in the present collection are identified as pertaining to Baena 



* Hay, 0. P., " Fossil Turtles of North America," Pub. Carnegie Institution, Washington, 1908, pp. 67-68. 



