4 8 



FOSSIL TURTLES OF NORTH AMERICA. 



specimens just mentioned. The number of the specimen is 336. It presents the shell complete, 

 the dorsal and the cervical vertebrae, the skull quite complete, the shoulder and pelvic girdles, 

 and portions of all the limbs. The skull will be described first. 



When buried the skull was undoubtedly complete, but has suffered somewhat during 

 disinterment and preparation (plate 5, figs. 3, 4). The bone is extremely brittle and much 

 fractured. On this account, and because ot the roughness of the surface, the sutures are mostly 



undeterminable. The length from the occipital 

 condyle to the end of the snout is 66 mm., nearly 

 the same as that of Marsh's specimen. In form it 

 is wedge-shaped, but not so narrow as Marsh's 

 laterally crusht specimen. The width at the 

 quadrates is 48 mm. The supraoccipital spine is 

 missing. It is doubtful whether it ever had any 

 considerable length. The parietals lack about 5 

 mm. of extending backward as far as the occipital 

 condyle. The roofing of the temporal region is 

 like that of the skull just described. Whether or 

 not the parietals join the squamosals can not be 

 determined; they probably do. The orbits had a 

 diameter of 15 mm., but some allowance must 

 be made for distortion; they appear to have 

 been larger than those of Marsh's type. The 

 interorbital space measures 9 mm. Apparently 

 the sutures bounding the frontals laterally can be 

 distinguish!, and possibly those limiting these 

 bones anteriorly. Nasal bones can not be distin- 

 guish!. The maxillary bone is only 3 mm. wide 

 below the orbit. The tympanic cavity appears to 

 have been small. The stapedial passage was open 

 behind. The quadrates appear to have been 

 directed slightly forward. The lateral squamosal 

 processes extend behind the occipital condyle 

 about 5 mm. 



On the upper surface there is observed on 

 each side a groove, or sulcus, which starts about 8 

 mm. from the midline at the hinder border of the 

 temporal roof, runs first forward and inward to 

 near the midline, then toward the orbit. Similar 

 sulci are seen in Chelydra and it is thus rendered 

 probable that the surface of the head was covered 

 with horny scutes. 



The basioccipital and the basisphenoid are 

 narrow. The suture between the two can not be 

 certainly distinguisht. The basisphenoid can be 

 traced forward about 30 mm. from the condyle. 

 It is 7 mm. wide posteriorly and narrows ante- 

 riorly. It is doubtful if the pterygoids came in 

 contact at any point. The pterygoid region, where 



narrowest, is 14 mm. wide. Toward the anterior 



end of the basisphenoid there is on each side, 



FIG. 17. Glyptops plicatulus. Carapace, xj. between this bone and the pterygoid, a foramen, 

 No. 336 A. M. N. H. Shows the various such as is seen in Baena, probably for the passage 

 bones and many of the scutes. of a vein. In the skull here described a groove 



FIG. 18. Glyptops plicatulus. Carapace, xj. proceeds backward for some distance, and the 

 N- 1357 Yale University. Shows only the appearance is such that the presence of a slit 

 bones. Figure from U. S. G. S. between the bones is suspected. The ectoptery- 



