Williston.] Turtles. 355 



and a little outward to join the nasal suture, as is indicated in 

 the drawing, thus excluding the prefrontals from meeting in 

 the middle line. 



With this interpretation, the prefrontals are small, and have 

 an irregularly four-sided shape. Their orbital margin is even 

 shorter than that of the frontals. 



The nasal suture is transverse ; the maxillary suture oblique 

 and gently concave. The superior aspect of each bone is on 

 one plane, sloping outward and forward. 



The nasals are united by well-marked sutures, and are sub- 

 quadrate in shape, the maxillary and prefrontal sutures, which 

 are nearly of the same length, meeting in an acute angle. There 

 may have been a slight notch in the middle in front. The 

 bones together form a very gentle arch. 



The premaxillaries show distinct sutures, both median and 

 lateral, the latter nearly at the outer margin of the narial open- 

 ing and all parallel. 



The postfrontals form an extensive arch, together with the 

 parietals, covering the temporal fossae. Their union with the 

 jugals is not evident, but seems to be above the middle of the 

 posterior orbital margin. The postfronto-squamosal suture is 

 likewise not distinct. 



The lower margin of the maxillaries forms a rather thin, some- 

 what sinuous edge. The junction with the jugal it is impossi- 

 ble to trace. On the posterior part, from near the middle 

 of the orbital margin, there was evidently a thin expansion 

 downward, but the edge has been broken off, so that one can- 

 not say to what extent. Its ascending process to join the pre- 

 frontals is about one inch in width between the nares and orbits. 



The external nasal opening is cordate in shape, with a rounded 

 anterior angle. The plane of its margins looks upwards and 

 forwards at an angle of about thirty-five degrees from the per- 

 pendicular. 



The posterior margin of the orbits is almost exactly in the 

 middle of the anterio-posterior diameter of the skull. Their 

 shape is irregularly oval, the greater diameter being from be- 

 fore back. Their superior margin, as far back as the fronto- 



