82 DEVELOPMENT OF THE SKELETON OF THE THAT ABA. 



PLATE IV. 



SPHENODON PUNCTATUS. DEVELOPING SKULL, LATER STAGES. 



an., angular ; r., articular ; b.o., basi-occipital ; b.s., basisphenoid ; b.sJ, basipterygoid 

 process ; c', anterior semicircular canal ; c.", posterior semicircular canal ; cr., coronoid ; 

 d., dentary ; e.c., extrastapedial cartilage ; e.n., external nares ; e.o., exoccipital ; e.p.g., epipterygoid ; 

 e.s., ethmosphenoidal plate; ex., extranasal; ex. l -ez. 5 , extranasal processes; f.i.-xii., foramina for 

 exit of cranial nerves /., fenestra in the suprastapedial cartilage ; f.e., ethmoidal foramen ; 

 /.i., interorbital fenestra ;/.;'., foramen for jugular vein; f.n., fenestra in the anterior wall of the 

 brain-case; f.p., parietal foramen; jr., frontal; h.' , anterior cornu of the hyoid; i.n., internal 

 nares; j., jugal; l.d., lachrymal duct; ink., Mocker's cartilage; mp., meniscus pterygoideus ; 

 mx., maxilla ; mx.', maxillary process ; n. v., vi., cranial nerves ; n.c., nasal capsule ; n.c.' ' , supra- 

 nasal process ; n.c.", prenasal process; nf.' } nf.", nasal fenestrse; ns., nasal; oc.c., occipital condyle; 

 op., opisthotic; o.s., otosphenoidal plate ; o.s. } ~', otosphenoidal processes ; p., parietal ; pa., palatine ; 

 p.f.y prefrontal ; p.g., pterygoid ; p.g.', pterygoid process ; p.o., postorbital ; po.f., postfrontal ; p.p., 

 parotic process ; pro., prootic ; ps., presphenoidal cartilage ; p.s., parasphenoid ; px., premaxilla ; 

 py., pituitary body ; q., quadrate; q. r , otic process of quadrate; q.j., quad rato-ju gal ; s.a., supra- 

 angular; sb., subnasal ; s.i., interorbital septum; s.mx., septo-maxillary ; s.o. } supra-occipital; 

 s.o.', supra-occipital cartilage; sp., splenial ; sg., squamosal ; sq.' , anterior process of squamosal; 

 sq.", posterior process of squamosal: s.st., suprastapedial cartilage; st., stapes; t.p., trans- 

 palatine ; vo., vomer. 



Fig. 1 . Stage R-S. The head : Transverse section through epipterygoid region (7-8 of fig. 4) . 



X 6. 

 Fig. 2. Stage R-S. The same : Combined figure of two transverse sections through the nasal 



region (a-/3 of fig. 4), the left half several sections in front of the right, x 15. 

 Fig. 3. Stage R-S. The same : Transverse sections showing detailed relations of pterygoid and 



basisphenoid (seven sections in front of fig. 1). x 18. 



Fig. 4. Stage S. Developing skull : Lateral aspect. X 5. 



Fig. 5. Stage S. The same : Dorsal aspect. X 5. 



Fig. 6. Stage S. The same : Ventral aspect. x 5. 



Fig. 7. StageS. The same: Posterior aspect. x 5. 



Fig. 8. Stage T. Developing skull : Dorsal aspect. x 3. 



Fig. 9. Stage T. The same : Posterior aspect. X 3. 



Fig. 10. Stage T. The chondrocranium : With endostoses and the parasphenoid ; as seen after 



removal of the mandibular skeletal arch. Left lateral aspect. x 3. 



Fig, 11. Stage T. The left pterygo-quadrate arch and squamosal : Lateral aspect. x 5. 



