THE SKELETON OF THE FROG. THE SKULL. 155 



and opisthotic elements of many skulls, in addition to the 

 exoccipitals. 



The patch of unossified cartilage immediately external. to 

 the occipital condyle is pierced by two small foramina, through 

 which the ninth and tenth nerves leave the cranial cavity. 

 The ninth nerve passes through the more external of these 

 foramina, the tenth through the one nearer the condyle. 



A B 



20 



FlG. 24. A DORSAL, AND B VENTRAL VIEWS OF THE CRANIUM OF A 



COMMON FROG (Rana temporaria) x 2 (after PARKER). 



In this and the next two figs, cartilage is dotted, cartilage bones are 

 marked with dots and dashes, membrane bones are left white. 



1. sphenethmoid. 



2. fronto-parietal. 



3. pterygoid. 



4. squamosal. 



6. exoccipital. 



7. parasphenoid. 



8. pro-otic. 



9. quadratojugal. 



10. maxilla. 



11. nasal. 



12. premaxilla. 



13. anterior nares. 



14. vomer. 



15. posterior nares. 



16. palatine. 



18. columella. 



19. quadrate. 



20. occipital condyle. 

 II. optic foramen. 



V. VII. foramen for exit of 

 trigeminal and facial nerves. 



IX. X. foramina for exit of glos- 

 sopharyngeal and pneumogastric 



