87 



pedicels of the quadrates. There appears to have been only a rudimentary ridge on the 

 triturating surface. The sutures between most of the bones may be traced, but those separating 

 the frontals from the parietals have not been observed. Nasals were quite certainly present, but 

 they are broken away. The lower jaw is present (fig. 75). The triturating surface is trans- 

 versely concave and 9 mm. wide. The tip of the jaw is damaged so that the length of the 

 symphysis can not be exactly determined; but it was not far from 15 mm. 



Chisternon hebraicum Cope. 

 Plate 21, figs. 3, 4; plate 23, fig. i; teit-figs. 76-87. 



Baena hebraica, COPE, Palaeont. Bull. No. I, 1872, p. 463; Proc. Amer. Philos. Soc., xil, 1873, p. 463; 

 6th Ann. Report, U. S. Geol. Surv. Terrs., 1872 (1873), p. 62; Vert. Tert. Form. West, 1884, p. 146, 

 plate xix, figs. I, 2. HAY, Bibliog. and Cat. Foss. Vert. N. A., 1902, p. 438. 



Baena undata, HAY, Bull. Amer. Mus. Nat. Hist., XXI, 1905, p. 138, figs. 1-3. 



Professor Cope's type of the present species consists of about two-thirds of the anterior 

 portion of the carapace and the plastron. It was obtained by him in the Bridger Badlands 

 along Cottonwood Creek, Wyoming, and hence in the level known as B. This type is now in the 

 U. S. National Museum at Washington. It appears to be necessary to correct some of Cope's 



measurements. The transverse axial width 

 is given by him as 500 mm., but it is only 

 420 mm. Accordingly, Cope's figures are 

 just one-third the size of nature. Cope's 

 estimate of the length was also 500 mm., 

 but the writer would make it only about 425 

 mm. In either case the shell is about as 

 broad as long. The length of the anterior 

 lobe of the plastron, to a line joining the 

 bottoms of the axillary notches, is 125 mm. 

 Its width is 147 mm. The bridges are 162 

 mm. wide. The hinder lobe has a basal 

 width of 160 mm. 



As shown by Cope's figures, the nuchal 

 and the anterior marginal scutes have small 

 extent at right angles with the free border, 

 and the first vertebral is transversely divided 

 so as to make 6 vertebrals in all. The margi- 

 nals over the bridges are higher than long, 

 and the corresponding costal scutes become 

 thereby about as high as long. There is 

 likewise a supernumerary costal scute on 

 each side of the first vertebral. 

 The shoulder-girdle is present, but has not been wholly freed from the matrix. The 

 scapula is at least 90 mm. long from the glenoid fossa to the upper end. At its base the cora- 

 coid has a diameter of 7 mm.; at a distance of 65 mm. from the glenoid fossa the diameter is 

 65 mm. 



No. 5961 of the American Museum is referred to this species. It was collected in 1903 by 

 Mr. L. S. Quackenbush, a member of the museum's party. The locality is Grizzly Buttes, 

 not far from the locality where Cope's type was collected. It was found lying in close prox- 

 imity with the specimen numbered 5962 and referred to Leidy's Chisternon undatum. Both 

 specimens furnisht good skulls and other skeletal parts. Figure 76 represents the carapace 

 of No. 5961; fig. 77, the plastron. The shell, especially in the region of the distal ends of the 

 costals, is thin and fragile and some parts were lost. The right half of the nuchal is gone, the 

 rear of the carapace is missing. 



The axial length of the carapace was close to 474 mm. ; the greatest width 435 mm. It was 

 moderately convex. The surface is nearly smooth. Along the areas of the vertebral scutes 

 are some traces of the sculpture so conspicuous in the case of species of Baena. Across some of 



FlG. 76. Chisternon hebraicum. Portion of carapace. 

 Xi No. 5961 A. M. N. H. 



e. p. I, front costal plate; c. s. I, first costal scute; n. I, n. 2, 

 neural bones; pren, preneural. 



