TOXOCHF.LYID^:. 183 



The skull is broad and it was probably originally considerably deprest, but to what extent 

 the present flatness is due to pressure can not be determined. The outlines as seen from above 

 (fig- 2 35) are greatly like those of Porthochelys laticeps, but the skull of the present species 

 is longer than broad. The sides of the skull converge slowly to the front of the orbits, where the 

 width is still 100 mm., then rapidly approach the tip of the snout. The outline is such that the 

 snout appears somewhat produced. The occipital condyle is broken away, but from its esti- 

 mated position to the end of the snout is 160 mm.; from the end of the supraoccipital spine to 

 the snout, 190 mm. The breadth from the outside of one quadrate to that of the other is 142 

 mm. The bones of the upper surface of the skull are smooth, whereas those of P. laticeps are 

 ridged and grooved. The temporal region is rooft over not quite as far backward as the 

 hinder borders of the exoccipitals and paroccipitals, so that the latter bones are seen from above. 

 Hence, the roof is not so extensive as in Chelonia mydas, but about as complete as in Caretta. 



FIG. 235. Porthochelys browni. Skull of type, upper aspect, xi. No. 6080 A. M. N. H. 

 fr, frontal; ju, jugal; mx, maiilla; pa, parietal; pof, postfrontal; prf, prefrontal; sq, squamosal. 



The eyes of this turtle were evidently directed strongly upward as well as outward. The 

 distance from the middle of the lower part of the rim of one orbit to that iof the other is 90 mm. 

 The width of the interorbital space is 30 mm. If now the middle of the interorbital space 

 stood 50 mm. above the roof of the mouth the plane of the orbits would stand at an angle ot 

 45 with the horizontal. It is not probable that the elevation of the skull was greater than that 

 supposed. The longitudinal diameter of the orbit is 50 mm. The transverse diameter of one 

 is now 33 mm., of the other 30 mm. If the elevation of the skull was originally 50 mm. above 

 the roof of the mouth the transverse diameter of the orbit must have been about 43 mm. It 

 is not likely to have been more. Hence, we seem to be justified in believing that the eyes were 

 directed strongly upward. 



It is evident that the nasal opening was higher than wide. Its present width is 19 mm., its 

 height 21 mm. The distance from the orbit to the hinder border of the temporal roof is 53 mm. 



The anterior borders of the choanae are placed 43 mm. behind the tip of the snout (fig. 236). 

 The palatines appear to have joined the vomer, as in Toxochelys. The crushing-surfaces of 

 the upper jaws have a width of about 27 mm. They are concave from the cutting-edge of the 

 jaw to the palatines. The width of the combined pterygoids, where narrowest, is 39 mm. 



