BAENID^. 73 



pendicularly, while the horizontal diameter is only 14 mm. The narial opening is 21 mm. wide 

 and it looks strongly upward as well as forward. The bones roofing it are 6 mm. thick. The 

 tympanic region is damaged, but the vertical diameter was 20 mm. The quadrate is deeply 

 notcht for the passage of the stapedial rod. 



At their narrowest part the pterygoids are 14 mm. wide. There are large postpalatine 

 foramina. The front of the choanae is placed 17 mm. behind the premaxillae. The cutting- 

 edges of the maxillae converge at nearly right angles. The triturating surface is 7 mm. wide. 

 Af its inner border, on each side of the choanae, arises a sharp crest. These crests converge to 

 the front of the choanae, then run parallel to near the premaxillae, thus producing a deep 

 groove in front of the choanx. 



O 



The lower jaw (plate 14, figs. 5, 6) is thick and heavy. From the middle of a line joining 

 the front borders of the articulation for the quadrates to the tip of the jaw is 40 mm. This line 

 prolonged backward even with the extremities of the rami would measure about 52 mm. while 

 the greatest width was 60 mm. The triturating surfaces are concave transversely, and are 7 

 mm. wide. The middle of each ramus is 9 mm. thick and 15 mm. high. The tip of the jaw is 

 turned upward, beak-like. The length of the symphysis on the lower side is 21 mm. 



The upper surface of the skull was undoubtedly covered with numerous horny scutes. 

 These are shown, as far as determined, in plate 13, fig. i. They are somewhat irregular in 

 form and disposition, but there is no difficulty in making out some symmetry in their arrange- 

 ment. The horny covering of the maxillae appears to have been divided, for a deep sulcus runs 

 downward from the front of the orbit to the cutting-edge. 



56- 



55- 



FlGS. 54-56. Baena sima. No. 5907 A. M. N. H. 

 54. Pelvis, right side. Xi- 56. Digit. X- 55- Distal end of humerus. Xj- 



Accompanying the shell of this specimen are various portions of the internal skeleton, 

 mostly fragmentary, however. The left humerus is represented by the proximal and the distal 

 ends. The proximal shows a width, from the outside of the ulnar to the outside of the radial 

 process, of 33 mm., a single millimeter more than in the specimen of B. arenosa, No. 5973, 

 above described. Nevertheless, the long diameter of the head is 14.5 mm.; that of No. 5973, 

 13 mm. The ulnar process has a thickness of 1 1 mm.; that of No. 5973 a thickness of 9 mm. 

 The distal end of this bone is 27 mm. wide. The trochlea has a narrow rounded ridge for the 

 head of the radius and a broader one for the head of the ulna, the two being separated by a 

 groove. Above the trochlea is a deep olecranon depression. The prepubic process resembles 

 that represented in fig. 86, but it is thin and flat. With this specimen are found 3 conical dermal 

 bones whose bases were buried in the skin, the remainder being covered with horn. Two of 

 these are symmetrical and may have been placed on the midline of the upper side of the tail, as 

 in Chelydra. However, they are not comprest, but circular in section. The base of one is 10 

 mm. in diameter and the height is the same; the other is smaller. The third is unsymmetrical 

 and somewhat flattened. It is possible that on the tail were 3 rows of dermal bones or there 

 may have been dermal bones on the legs, as in some species of TestuJo. 



No. 5965 may be regarded as the paratype of the present species. It furnishes only the 

 carapace and plastron. It was secured in 1903, at Grizzly Buttes, Wyoming. The carapace is 

 more complete than that of the type and has furnisht plate 15. The length is 333 mm. along 



