In a median longitudinal section of the skull the hypoglossal foramen is seen, and just in front of it a small foramen for a vein. Further forwards the long slit-like opening between the exoccipital and opisthotic is the =internal auditory meatus= (fig. 45, VIII) through which the auditory nerve leaves the cranial cavity and enters the internal ear.
The =supra-occipital= (fig. 45, 5) is a small bone which takes no part in the formation of the foramen magnum, and is closely united in front with the epi-otic. It is characteristic of Crocodiles that all the bones of the occipital segment have their longer axes placed vertically, and that they scarcely if at all appear on the dorsal surface.
In front of the occipital segment is the =parietal segment=. The dorsal and ventral portions of the two segments are in contact with one another, but the lateral portions are widely separated by the interposition of the =auditory= and =suspensorial bones=.
The =basisphenoid= (fig. 45, 12) is an unpaired wedge-shaped bone, united along a deep vertical suture with the basi-occipital. The two bones are, however, partially separated in the mid-ventral line by a foramen, the opening of the =median Eustachian canal=, which leads into a complicated system of Eustachian passages ultimately communicating with the tympanic cavity.
The dorsal surface of the basisphenoid is well seen in a section of the skull, but owing to the way it tapers ventrally, it appears on the ventral surface only as a very narrow strip of bone wedged in between the basi-occipital and pterygoids. In a lateral view it is seen to be drawn out in front into an abruptly truncated process, the =rostrum=, which forms part of the =interorbital septum.= On the anterior part of the dorsal surface is a deep pit, the =pituitary fossa= or =sella turcica=, at the base of which are a pair of foramina, through which the carotid arteries pass. Dorsolaterally the basisphenoid articulates with the =alisphenoids=.
[Illustration FIG. 44. LATERAL VIEW OF THE SKULL OF AN ALLIGATOR (_Caiman latirostris_). × 1/3. (Brit. Mus.)
1. premaxillae. 2. maxillae. 3. lachrymal. 4. prefrontal. 5. jugal. 6. postfrontal. 7. squamosal. 8. quadrate. 9. palatine. 10. pterygoid. 11. transpalatine. 12. quadratojugal. 13. exoccipital. 14. basi-occipital. 15. foramen by which carotid artery enters skull. 16. external auditory meatus. 17. frontal. 18. supra-angular. 19. articular. 20. dentary. 21. coronoid. 22. angular. III, VI, opening for exit of oculomotor and abducens nerves. V, foramen ovale. X, pneumogastric foramen. XII, hypoglossal foramen.]