Description of Plate 21. 



BONES OF CROTALUS ADAMANTEUS 



A. Ventral view of skull. Other bones, right side seen from inside. 



1. Premaxillary bone. 



2. Prefrontal, or lacrymal, bone. 



3. Frontal bone. , 



4. Post-orbital process. 



5. Posterior region of parietal bone. 



6. Crest of sphenoid bone. 



7. Squamosal bone. 



8. Articulating surface of supermaxillary bone (with prefrontal bone, 2). 



9. Foramen for entrance of a large branch of trigeminous (into the pit). 



10. Supermaxillary bone. 



11. Palatine bone. 



12. Poison fang. 



13. Internal pterygoid bone. 



14. External pterygoid bone (so-called transversum). 



15. Quadrate bone. 



16. Mandibular bone. 



B. Dorsal view of skull. Other bones, right side, seen from outside. 



17. Occipital bone. 



18. Articulating surface of temporal bone (with squamosal bone, 24). 



19. Parietal bone. 



20. Frontal bone. 



21. Premaxillary bone. 



22. Prefrontal, or lacrymal, bone. 



23. Post-orbital process. 



24. Squamosal bone. 



25. Quadrate bone. 



26. Mandibular bone. 



27. Internal pterygoid bone. 



28. External pterygoid bone (or the transversum). 



29. Palatine bone. 



30. The pit of the supermaxillary bone (the foramen for the nerves is seen in the upper 



position of the pit). 



31. Supermaxillary bone. 



32. Poison fang. 



