246 THE FIFTH DAY. [CHAP. 



Farts of the bird's skull which are either preformed 

 in cartilage or remain cartilaginous. 



Formed from the parachordal cartilages and their 

 upgrowths around the foramen magnum. — Supraocci- 

 pital. Exoccipital. Basioccipital. 



Formed in the periotic cartilage. — Epiotic. Prootic. 

 Opisthotic. 



Formed from the trabeculae and their upgrowths. 

 — Alisphenoid. Basisphenoid. Orbitosphenoid. Pre- 

 sphenoid. Ethmoid. Septum nasi, turbinals, prenasal 

 and nasal cartilages. 



Articulare and quadrate belonging to the first 

 visceral arch. Skeleton of the second and third visceral 

 arches and stapes. 



Splint-bones not preformed in cartilage. 



Parietals. Squamosals. Frontals. Lacrymals. 

 Nasals. Premaxillae. Maxillae. MaxUlo-palatiues. 

 Vomer. Jugals. Quadrato-jugals. Dentary and 

 bones of mandible. Basi- temporal and rostrum. Ptery- 

 goid and palatine (superior maxillary process). 



The face. Closely connected with the development 

 of the skull is the formation of the parts of the face. 



After the appearance of the nasal grooves on the 

 fourth day the mouth (Fig. 80, M.) appears as a deep 

 depression inclosed by iive processes. Its lower border 

 is entirely formed by the two inferior maxillary pro- 

 cesses (Fig. 80, F. 1), at its sides lie the two superior 

 maxillary processes S. M., while above it is bounded by 

 the fronto-nasal process nf. 



