1896. SKELETON OF TOXOCHELYS HAY. 103 



5. The structure and the connections of the anterior ends of the 

 pterygoids are greatly like those of the Chelydridw. The ectopterygoid 

 processes are prominent, their posterio-external angle directed back- 

 ward, and their outer border broad for muscular attachment, just as 

 in Chelydra. 



6. The orbits are of moderate size, being intermediate between 

 those of Chelydra and Chelonia. The plane of the rim has been di- 

 rected, as in Chelydra, outward and upward. In this respect the orbits 

 resemble those of Chelydra, but not those of Macrochelys. In this genus 

 the orbits appear to have been given a perpendicular rim through the 

 excessive narrowing of the snout, just as is also the case with Eretmo- 

 chelys. 



7. The external border of the pterygoid bone runs backward as 

 a sharp keel terminating on the mesial side of the pedicel of the quad- 

 rate. In this arrangement Toxochleys resembles Chelydra, Thalasso- 

 chelys, Lepidochelys, and Eretmochelys, but not Chelonia. In the last 

 genus the external border of the palatal portion of the pterygoid 

 ceases abruptly on the under side of that portion of the bone which 

 lies between the quadrates, thus leaving a broad notch in the ptery- 

 goid. 



8. That portion of each pterygoid which lies between the quad- 

 ratic pedicels is furnished with a broad groove which terminates 

 posteriorly behind the inner border of the pedicel. This groove does 

 not appear to have had any considerable depth, but some allowance 

 must be made for the effects of pressure. In Chelydra this region is 

 flat and smooth; in Chelonia it is also nearly flat, while the border is 

 notched. 



9. Between the posterior ends of the pterygoidean grooves, on 

 the basisphenoid and the basioccipital, is found an elevated triangu- 

 lar rough surface for the attachment of muscles. A similar surface is 

 found here in all the Cheloniidce, but not in the Chelydrida. 



10. In Chelonia, there is found below and behind each jugular 

 foramen a strong process into which enter the basioccipital, the exocci- 

 pital, and the pterygoid. This process is wanting in the Chelydridcc 

 and most other turtles, but is present in the Cheloniida. It was well 

 developed in Toxychelys. In the Chelydrid(e\\\z exocipital contribution 

 to this process is well developed and its outer extremity extending 

 across the jugular foramen joins the paroccipital, thus cutting off a 

 portion of the jugular foramen as a special pneumogastric foramen. 

 In Toxochelys the arrangement of the parts is as in Chelonia. 



11. The tympanic cavity closely resembles that of Chelonia. It 

 has, however, been extended downward further on the pedicel of the 

 quadrate, since this is distinctly concave nearly to the articulate 



