97] THE SKULL OF AM lURUS— KINDRED 97 



this immediate region could not be clearly made out. The two pairs of myo- 

 tomes following these are innervated by the second and third pa"rs of post-vagal 

 nerves. 



9. The beginnings of the premaxillary and maxillary bones are present in 

 the 8 mm. Amiurus. 



10. The palatine cartilage is independent of the pterygoquadrate, and the 

 latter is fused to the hyomandibular. 



11. Ossification is present in the skull of the 32 mm. Amiurus. The large 

 dorsal fontanelles of the 10 mm. stage are limited to mere slits by the frontal and 

 supraoccipital ossifications; the epiphysial cartilage persists, but lies relatively 

 further posterior; a rudimentary tegmen cranii and synotic tectum are present; 

 a massive cartilaginous internasal septum divides the olfactory tracts; the 

 olfactory foramina lie in a transverse plane. 



12. The supraethmoid bone has both membrane and perichondrial ossifica- 

 tions entering into its composition. The perichondrial ectethmoid ossification 

 is fused with a connective tissue ossification on the lateral margin of the 

 ectethmoid process. The foramen orbito-nasale lies relatively more posterior 

 than in the 10 mm. stage; perichondrial ossifications appear on the margin of 

 the orbital foramen. 



13. The fenestra hypophyseos is closed by the orbitosphenoid, parasphenoid, 

 suprasphenoid, and prootic ossifications. 



14. The intercranial extent of the notochord is apparently less than in the 

 10 mm. stage, but this is due to the greater relative growth of the cartilaginous 

 parts surrounding it. 



15. The suprasphenoid bone is developed from membrane in the floor of the 

 cranium and is not the homologue of the basisphenoid of the mammahan cra- 

 nium, but is a bone peculiar to the teleosts. 



16. A squamosal ossification, developed from membrane, fuses with the 

 pterotic ossification; as the latter has no homologue in the mammalian petrosal, 

 the resulting bone of the adult cannot be a temporalis, but must be regarded as 

 a squamoso-pterotic. 



17. The spina occipitis of the supraoccipital bone arises from membrane and 

 is the homologue of the supraoccipital plates of the Stegocephali and probably 

 of the interparietal element of the mammalian cranium. 



18. The skull of the adult Amiurus is well ossified, although considerable 

 cartilage persists in the ethmoid and otic regions. The adult cranium resembles, 

 in many points, the crania of some of the Characinidae and Cyprinidae. 



