i86 



KOSSII. TURTLES OF NORTH AMKRICA. 



deposits, near Fairbury, Nebraska. An extended description of the species, with figures, is 

 given by Williston, as cited above. A number of his drawings have been reproduced in the 

 present work. 



This turtle was evidently a large one. The skull (figs. 238, 239) is uncrusht, but the hinder 

 portion of the base is damaged. The total length from the snout to the end of the supraoc- 

 cipital spine is 205 mm.; the width thru the quadrates is 145 mm. The skull is remarkable 

 for the length of the posterior lateral, or squamosal, processes. These lack but little of extend- 

 ing backward as far as the supraoccipital process; while the latter has about its usual length. 

 The parietals are unusually narrow. Williston informs us that these bones join the squamosals. 

 The frontals and the prefrontals together occupy the area occupied in Chelonia myJas by the 

 frontals. In front of the prefrontals come the large nasals, bones rarely found in Cryptodira. 

 These nasals are about 13 mm. long and each is about 19 mm. wide. The antero-posterior 



240. 



FIGS. 240-243. Dfsmatochelys lowi. Portions of the type. 



240. Humerus. 



241. Pelvic bones. /'/, ilium; isch, ischium; pub, pubis. 



242. Fragments of peripheral bones. 



243. Fragments of plastron and peripheral bones. 



diameter of the nasal opening is 24 mm.; the transverse diameter, 18 mm. It looks strongly 

 upward. The orbits have an antero-posterior diameter of 60 mm. The interorbital space is 

 58 mm. wide. 



The palate (fig. 239) is remarkable on several accounts. The choanae are considerably 

 further forward than they are in the Cheloniidae; but what is more important, there is no floor 

 beneath them formed by the bones bounding them. Each is at the anterior end of a longitudinal 

 concavity, whose depth diminishes backward. The transverse sutures between the palatines 

 and the pterygoids are relatively much further backward than they are in Chelonia mydas. 

 The pterygoid processes are therefore more posterior than usual. The possession of posterior 

 palatine foramina is another feature distinguishing this species from any of the modern sea- 

 turtles. They are small, and may be regarded as vestigial. Behind the pterygoid processes 

 the palate narrows to a width of about 22 mm. In front of the processes named there is another 

 slight constriction of the palate. The longitudinal median sutures are not discernible, and it 

 is not certain that the palatines joined in the midline. 



