82 DEVELOPMENT 01'' THE SKELETON oK TIIH TL''ATARA. 



PLATE IV. 



SpHENODON PL'NCTATUS. — DEVELOPING SKULL, LATER STAGES. 



cm., angular; ur., articular; /j.o., basi-occipital ; b.s., basisphcnoid ; l/.sj, basipterygoid 

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

 (I., dcutary; e.f., extrastapcdial cartilage; e.w., external uares; e.o., exoccipital ; e./>.^., epiptcrygoid ; 

 e.g., ethmosplicnoidal plate; ex., extranasal; ex.^-ex.', extranasal processes; f.i.-xii., foramina for 

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

 /./., iutcrorbital fenestra;/^'., foramen for jugular vein; f.ii., fenesti'a in the anterior wall of tlie 

 braiu-casc; /.p., parietal foramen; fr., frontal; h.', anterior cornu of the hyoid; i.n., internal 

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

 »(,r., maxilla; ?>w.'.', maxillary process; n. v., vi., cranial nerves; «.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 ; 0.5.''', otosphenoidal processes ; p., parietal ; pa., palatine ; 

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

 ])arotic process; pro., prootie ; j}s., presphenoidal cartilage ; p.s., parasphenoid ; px., premaxilla; 

 ^;y., pituitary body ; q., quadrate; 5'.', otic process of quadrate; (Z^;'., quadrato-jugal ; .9. a. , supra- 

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

 s.o.', supra-occipital cartilage; s/>., splenial ; sq., squamosal; s^r.', anterior process of squamosal; 

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

 palatine ; vu., vomer. 



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



X fi. 



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



region (a-yS 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 



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



Stage S. Developing skull : — Lateral aspect. X 5. 



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



Stage S. The same : — Ventral aspect. x 5. 



Stage S. The same: — Posterior aspect. X 5. 



Stage T. Developing skull : — Dorsal aspect. X 3. 



Stage T. The same : — Posterior aspect. X 3. 



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



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



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



Fig. 



4. 



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5. 



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7 . 



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10. 



