68 



FOSSIL TURTLES OF NORTH AMERICA. 



obtained at Church Buttes, in the level known as B. Dr. Leidy's figure makes the anterior 

 lobe of the plastron appear too short and too narrow. The plastron has a total length of 275 

 mm. The anterior lobe is 75 mm. long and 70 mm. wide at the base. The bridge has a width 

 of 123 mm. The hinder lobe is 77 mm. long and 1 10 mm. wide at the base. The carapace has 

 .1 length of 300 mm. in a straight line. The surface is uneven, especially within the areas of the 



vertebral scutes. There appear to have been no supernumer- 

 ary costal scutes. The dimensions ot the vertebrals are given 

 in the accompanying table. 



The American Museum expedition of 1903 collected a 

 number of specimens which must be referred to this species. 

 The most important of these is No. 5973, collected at Grizzly 

 Buttes, Wyoming. It furnishes a somewhat damaged shell; 

 the skull, lacking the left side and the lower jaw; a portion of 

 the shoulder-girdle; the humerus, lacking the distal end; and 

 the ulna. The length of the carapace (plate 12) in a straight 

 line is 330 mm., to the bottom of the posterior notch, 320 mm.; 

 its width, about 315 mm. The bones are thoroly co-ossified 

 and the sutures obliterated. The anterior border projects somewhat at the midline. The pos- 

 terior border is broad, with a median excavation 60 mm. wide and lateral scallops. 



48- 



+6. 



44- 47- 



Figs. 44-48. Baena arenosa. No. 5973 A. M. N. H. 



+4. Pelvis teen from left side. X|. 



45. Left half of pelvis seen from below. 



46. Plastron. Xj. 



X? 



47. Left humerus. X- 



48. Right ulna. Xj- 



( )n each side of the first vertebral there is a small supernumerary costal scute. Along the 

 midline there is a narrow ridge and within the areas of the vertebral scutes a number of sym- 

 metrically arranged ridges. The dimensions of the vertebrals are given in the table above. 



I he plastron (plate 13, fig. 1 ; text-fig. 46) is 287 mm. long. The anterior lobe is jy mm. 

 long; 104 mm. wide at the base; and jj mm. at the gulo-humeral sulcus. The limits of the 

 entoplastron can not he traced. The bridge is 1 25 mm. wide. By means of the striations on the 



