80 DEVELOPMENT OF THE SKELETON OF THE TUATARA. 
PLATE III. 
SPHENODON PUNCTATUS.—DEVELOPING SKULL, EARLIER STAGES. 
The figures on this Plate are of wax models reconstructed from microscopic sections, 
the skeletal parts being alone represented. The fenestre and interspaces in the 
chondrocranium are for the most part occupied by membrane (not indicated), except 
in so far as they transmit nerves and blood-vessels (cf. Pl. 1V. fig. 10). 
an., angular; ar, articular; 6.s.', basipterygoid process; c.', anterior semicircular canal ; 
c.au., auditory capsule; ¢.r., coronoid ; d., dentary ; e.c., extrastapedial cartilage ; ¢.n., external 
nares; €.0., exoccipital ; epg., epipterygoid ; e.s., ethmosphenoidal plate; ex., extranasal; ew.'*, 
extranasal processes ; f.i.—vii., foramina for exit of cranial nerves; f.a., foramen for ophthalmic 
branch of the carotid; f.e., ethmoidal foramen ; f.i., interorbital fenestra; fj., foramen for jugular 
vein; f.m., foramen magnum ; f.n., lateral cranial fenestra; fr., frontal; 4., hyoid; f.’, anterior 
cornu of the hyoid; 4.", posterior cornu of the hyoid; i.n., internal nares; 7., jugal; mk., Meckel’s 
cartilage; mz., maxilla; mz.’, maxillary process; n.a.p., alinasal process ; xc., notochord ; n.c., nasal 
capsule; 2.c.', supranasal process; n.c.", prenasal process; n.f.', nasal fenestra; n.pa.p., naso- 
palatine process; n.p.p., naso-premaxillary process; ms., nasal; 7.v.p., inferior naso-vomerine 
process ; oc.c., occipital condyle ; os., otosphenoidal plate ; os.+°, otosphenoidal processes ; 
p., parietal ; pa., palatine; par., parachordal; p.f., prefrontal; pg., pterygoid; pg.', pterygoid 
process ; p.o., postorbital ; po,f., postfrontal; p.p., parotic process; p.g., pterygo-quadrate ; 
ps., presphenoidal cartilage ; p.s., parasphenoid; pw., premaxilla; py.', pituitary foramen ; 
qg., quadrate ; q.’, otic process of quadrate; g.j., quadrato-jugal ; s.a., supra-angular; sb., subnasal ; 
Sj,, interorbital septum; s.mz., septo-maxillary; s.0.’, supraoccipital cartilage; sp., splenial ; 
sq., squamosal ; sqg.”, posterior process of squamosal ; s.s¢., suprastapedial cartilage ; s¢., stapes ; 
t.p., transpalatine ; ¢7., trabecula; vo., vomer. 
Fig. 1’. Stage P. Developing chondrocranium :—Left lateral aspect. The arrow indicates the 
direction of the longitudinal axis of the embryo as it lay coiled. 54 Is}. 
Fig. 2'. Stage P. The same :—Ethmoidal, trabecular, and sphenoidal regions, dorsal aspect. x 13. 
Fig. 8°. Stage P. The same :—Parachordal and auditory regions, dorsal aspect. Sg 113%, 
Fig. 4. Stage Q. Developing chondrocranium :—Lateral aspect. x 8. 
Fig. 5. Stage Q. Developing skull :—Lateral aspect. x 8. 
Fig. 6. Stage Q. Developing chondrocranium :—Ventral aspect. x 8. 
Fig. 7. Stage Q. The same :—Dorsal aspect. DES: 
Fig. 8. Stage R. Developing chondrocranium :—Lateral aspect. x 8. 
Fig. 9. Stage R. Developing skull :—Posterior aspect. x 8. 
Fig. 10. Stage R. The same :—Uateral aspect. x 8. 
Fig. J1. Stage R. The same :—Dorsal aspect. x 8. 
Fig. 12. Stage R. The same :—Ventral aspect. x 8. 
* In these figures the uncoloured areas represent pro-cartilage. 
