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DEVELOPMENT OF THE SKELETON OF THE TUATARA. 
FLEADE LY, 
SPHENODON PUNCTATUS.—DEVELOPING SKULL, LATER STAGES. 
an., angular; ar., articular; b.0., basi-occipital; 4.s., basisphenoid; 4.s.', basipterygoid 
process; c.', anterior semicircular canal; c.", posterior semicircular canal; cr., coronoid ; 
d., dentary ; ¢.c., extrastapedial cartilage ; e.v., external nares ; ¢.0., exoccipital ; e.p.g., epipterygoid ; 
é.s., ethmosphenoidal plate ;“ex., extranasal; ex.'-ex.’, extranasal processes ; f.i.—vii., foramina for 
exit of cranial nerves /f., fenestra in the suprastapedial cartilage; f.e., ethmoidal foramen ; 
fi. interorbital fenestra ; fj., foramen for jugular vein; f.n., fenestra in the anterior wall of the 
braiu-case; f.p., parietal foramen; /fr., frontal; f.', anterior cornu of the hyoid; é.v., internal 
nares; j., jugal; dd., lachrymal duct; mk., Meckel’s cartilage; mp., meniscus pterygoideus ; 
mex., maxilla; ma.', maxillary process; ”. v., vi., cranial nerves; n.c., nasal capsule; n.c.', supra- 
nasal process ; 7.c.”, prenasal process ; nf.’, nf.’, nasal fenestrae ; ns., nasal; oc.c., occipital condyle ; 
op., opisthotic ; 0.s., otosphenoidal plate ; 0.s.'”, otosphenoidal processes ; p., parietal ; pa., palatine ; 
pF, 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 ; qg.’, otie process of quadrate; g,j., quadrato-jugal; s.a., supra- 
angnlar; sd., subnasal; s.i., interorbital septum; s.mz., septo-maxillary; s.0., supra-occipital ; 
s.o./, supra-occipital cartilage ; sp., splenial; sg., squamosal ; sq.’, anterior process of squamosal ; 
sq., posterior process of squamosal : s.s¢., suprastapedial cartilage; s¢., stapes; ¢.p., trans- 
palatine ; vo., vomer. 
Fig. 1. Stage R-S. The head :—Transverse section through epipterygoid region (y-6 of fig. 4). 
x 6. 
Fig. 2. Stage R-S. The same :—Combined figure of two transverse sections through the nasal 
region (a- of fig. 4), the left half several sections in front of the night. x 15. 
Fig. 8. Stage R-S. The same :—Transverse sections showing detailed relations of pterygoid and 
basisphenoid (seven sections in front of fig. 1). xls: 
Fig. 4. Stage S. Developing skull :—Lateral aspect. x Ob 
Fig. 5. Stage S. The same :—Dorsal aspect. 
Fig. 6. Stage S. The same :—Ventral aspect. x 5. 
Fig. 7. Stage S. The same:—Posterior aspect. x i, 
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 :—Uateral aspect. x 3. 
