37 



PLATE XIX. 



THE "FROG continued. 



SKELETON. 



%* The colours in left-hand corner of Plate refer only to Skull 

 THE BONY SKULL 



FIG. 1. DORSAL VIEW 



Exoccipitals (L. ex, out ; occiput, the back of the head). 

 Pro-otics (Gr. pro, in front of ; ous, otos, the ear). 



Parietals (L. paries, a wall) . . ) 



, /T ' , - , ,, > united in adult. 



1 ( rentals (L. frons, the forehead) ) 



Nasals. 



Premaxillae (L. prce, before ; maxilla, the upper jaw). 

 FIG. 2. VENTRAL VIEW, lower jaw removed 



Parasphen'oid (Gr. sphen, a wedge). 



Sphenethmoid or girdle-bone. 



Vomers with teeth. 



Premaxilke with teeth. 



Pterygoids (Gr. pteron, a wing). 



Palatines, slender palate bones. 

 FIG. 3. SIDE VIEW 



Squamosals. 



Quadrato-jugals. 



Maxillae with teeth. 



Premaxillae with teeth. 



Mandible or lower jaw, consisting of two rami (L. ramus, a branch) without teeth. 

 ( Meckel's cartilage forming the core. 



RAMUS 



\ Anarulo-splenial . . ) . 



i Dentary without teeth j mvestln S Meckels cartlla S c - 



V Mento-Meckelian bone (L. mentum, the chin), the ossified tip of Meckel's cartilage. 

 Fro. 4. POSTERIOR VIEW 



Exoccipitals with condyles (Gr. kondulos, a knuckle) for articulation with vertebral column. 

 Foramen magnum (L. great opening), through which spinal cord passes into brain. 

 THE CARTILAGINOUS SKULL 

 FIG. 5. DORSAL VIEW 



Sphenethmoid bone, replacing cartilage and partly covered by the f rentals (see fig. 1). 

 Nasal roof covered by nasals. 

 Fontanelles, membranous portions. 

 FIG. 6. VENTRAL VIEW 

 Sphenethmoid bone. 



Nasal floor anterior to Sphenethmoid covered by vomers. 

 Floor posterior to Sphenethmoid from the exoccipitals covered by the parasphenoid, which partly 



overlaps Sphenethmoid. 



Pterygoid bar, replaced by pterygoid and palatine bones (see fig. 2). 

 FIGS. 5, 6. MANDIBULAR SUSPENSORIUM, connecting lower jaw with skull- 

 Posterior end articulating with Meckel's cartilage. 



Anterior end dividing J Dorsal process or eras attached to outer wall of skull 

 into ( Ventral process or crus continuous with pterygoid bar. 



Note. Two kinds of bone are distinguished in the skull according to their mode ol origin 



1. Cartilage bones (red), as the nunic denotes, are first modelled in cartilage. 



2. Membrane or splint bones (blue) are those not so preformed in cartilage. 



