37 



PLATE XIX. 



THE FROG" — continued. 



SKELETON. 



*,* The colours iu left-hauJ corner of Tlate refer only to SkuIL 



TuE Bony Skull — 



Fig. L Doesal View — 



Exoccipitals (L. cr, out; occiput, tlie Lack of the head). 



Pro-otics (Gr. pro, in front of ; oiig, oios, the ear). 



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



■n- . , /T j> ii f 1 n • united m adult. 



i; rentals (L. frons, the lorenead) ) 



Nasals. 



Premaxilke (L. prce, before ; tnaxilla, the upper juw). 

 f IG. 2. Venteal View, lower jaw removed— 



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



Sphenethmoid or girdle-bone. 



Vomers with teeth. 



Premaxillae with teeth. 



Pterygoids (Gr. pteroii, a wing). 



Palatines, slender palate bones. 

 Fig. 3. Side View — 



Squamosals. 



Quadrato-j ugals. 



MasillEe with teeth. 



Premaxillre with teeth. 



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



/■ Meckel's cartilage forming the core. 



_ \ Angulo-splenial . . 1 . . ,, , ,, 



Kamtjs K t-v ^ ■ij^ ^ ^ fi f investing Meckels cartilage. 



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

 Fig. i. Posterior View — 



Exoccipitals with condyles (Gr. l-ondnlos, 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 jsartly covered by the froutals (see fig. 1). 

 Nasal roof covered by nasals. 

 Fontanelles, membranous jjortions. 

 Fig. 6. Ventral View^ 

 Sphenethmoid bone. 



Na.sal floor anterior to sphenethmoid covered by vomers. 

 Floor posterior to sphenethmoid from the exoccipitals covered by the parasphcnoid, which partly 



overlaps sphenethmoid. 

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

 Figs. 5, 6. Majmdibuxae Suspensoeium, connecting lower jaw with skuU — 

 Posterior end articulating with Meckel's cartilage. 



Anterior end dividing J Dorsal process or cms attached to outer wall of skulL 

 into ( Ventral process or crus continuous with pterygoid bar. 



Kote. — Two kinds of bone are distinguished in the skull according to their mode of origin — 



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



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



