22 F. B. Loomis — Turtles from the Upper Harrison Beds. 



and has a median ridge running from the basisphenoid onto 

 the premaxillse. The masticatory surface has three ridges and 

 two longitudinal furrows. The low, sharp outer ridge bounds 

 the jaw, overlapping the lower jaw but little. The middle 

 and inner ridges are still lower and rather obtuse. The median 

 ridge mentioned above as continuing onto the premaxillae 

 separates two deep pits, one on either side, which evidently 



Fig. 5. 



Fig. 5. Skull of T. brevisterna from above. % nat. size. 



Fig. 5a. The quadrate and otie region seen from the side to show the 

 narrow ear opening and the forward projection of the quadrate. % na ^ 

 size. 



received two horny teeth on the front of the lower jaw. There 

 is a strong ectopterygoid process on either pterygoid bone. 

 The opening for the ear is greatly narrowed, making a very 

 characteristic feature. (See fig. 5a.) 



Measurements. 



Length from the snout to the supra occipital crest __ 89 mm 



Length from the snout to the occipital condyle (estimate) . . 70 mm 



Width across the quadrates . _ 70mm 



Width of interorbital region ._ 25 mm 



Length of ear opening 14mm 



Height of ear opening 6 mm 



The short, widespread lower jaws have a longitudinal 

 groove bounded by sharp ridges of nearly equal height. The 

 jaw is 55 ram long and 19 mm high at the coronoid. 



The carapace is only 386 nim long and nearly as wide 

 (360 mm ), being high arched (148 mm high). The greatest width 

 is near the front and it narrows slightly as it approaches the 

 rear. The back of the shell drops off very abruptly, being 

 almost vertical, and extending below the plastron near the 

 middle line. The dimensions of the various plates appear in 

 the table below : 





