7° COMPARATIVE MORPHOLOGY OF VERTEBRATES. 
quadrate to form the functional upper jaw (figs. 66, 67) in all bony 
vertebrates. In its fullest development it consists of bones on either 
side, beginning behind with a squamosal, which overlies the quadrate, 
and followed by a quadratojugal, a zygomatic (malar or jugal), 
and a maxillary, which joins the premaxillary, the latter forming the 
Fic. 68.—Dorsal and ventral views of skull of young Sphenodon, after Howes and 
Swinnerton. Explanation of letters used in figures of skulls (figs. 68 to 105) unless other- 
wise stated. an, angulare; ao, antorbital; ap, antorbital process; ar, articulare; as, ali- 
sphenoid; 6, basale; bb, basibranchial; bh, basihyal; bo, basioccipital; bs, basisphenoid; 
cb, ceratobranchial; ch, ceratohyal; cl, columella; co, coronoid; cp, copula; cr, cranial rib; 
cr. eth, cribiform plate of ethmoid; d, dentary; de, dermal ethmoid; dee, dermal ectethmoid; 
eb, epibranchial; ee, ectethmoid; eh, epihyal; enp, entopterygoid; eo, exoccipital; ep, 
ectoptery goid; epo, epiotic; eth, ethmoid; ethpp; perpendicular plate of ethmoid; es, extra- 
scapular; exb, extrabranchial; /, frontal; /p, frontoparietal; g, goniale; k, hyoid; hb, hypohyal; 
hm, hyomandibular; hr, hyoid rays; 7, incus; if, infratemporal fossa; io, interoperculum; if, 
interparietal; j, jugal; /, lacrimal; Ja, labial; md, mandibular; me, mesethmoid; mk, Meck- 
elian; ml, malleus; mm, mentomeckelian; mpt, mspt, mesopterygoid; mtp, metapterygoid; 
mx, maxillary; mxp, maxillopalatine; mxt, maxilloturbinal; n, nasal; na, neural arch; nc, 
nasal capsule; 70, notochord; 9, occipital; oc, occipital condyle; 00, opisthotic; op, operculare; 
os, orbitosphenoid; of, otic bones; p, parietal; pd, predentary; pe, petrosal; pf, postfrontal; 
pl, palatine; pm, premaxillary; po, preoperculare; poo, postorbital; pg, pterygoquadrate; 
prf, prefrontal; pro, preorbital; prot, prootic; prs, presphenoid; ps, parasphenoid; pt, ptery- 
goid; ptc, pterygoid cartilage; pio, pterotic; g, quadrate; gj, quadratojugal; 7, rostral; rm, 
rostrum, sa, suprangulare; sbo, suborbital; sc, sagittal crest; scl, sclerotic; se, sphenethmoid; 
sf, supratemporal fossa; sh, stylohyal; so, supraoccipital; sop, subopereulare; sor, supra- 
orbital; sp, sphenoid; spht, sphenoturbinal; spi, splenial; spo, sphenotic; spt, supratemporal; 
sq, squamosal; ssc, suprascapular; st, stapes; sy, symplectic; ¢, temporal; ér, transversum; 
tu, turbinal; ty, tympanic; v, vomer; vp, vomeropalatine. 
tip of the jaw and meeting its fellow of the opposite side. Of these 
only the maxillary and premaxillary bear teeth. 
In the lower vertebrates the roof of the skull is continuous, its only 
openings being those for the nares and the orbits. In the higher 
