70 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 quadrate jugal, a zygomatic (malar or jugal), 

 and a maxillary, which joins the premaxillary, the latter forming the 



9 



FIG. 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; or, articulare; as, ali- 

 sphenoid; b, basale; bb, basibranchial; bh, basihyal; bo, basioccipital; bs, basisphenoid ; 

 cb, ceratobranchial; ch, ceratohyal; d, 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 ;fp, frontoparietal; g, goniale; h, hyoid;hb, hypohyal; 

 hm, hyomandibular; hr, hyoid rays; i, incus; if, infratemporal fossa; io, interoperculum; ip, 

 interparietal ; j, jugal; I, lacrimal; la, 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; no, notochord; o, occipital; oc, occipital condyle; oo, opisthotic; op, operculare; 

 os, orbitosphenoid; ot, otic bones; p, parietal; pd, predentary; pe, petrosal; pf, postf rental; 

 pi, palatine; pm, premaxillary; po, preoperculare; poo, postorbital; pq, pterygoquadrate ; 

 prf, prefrontal; pro, preorbital; prot, prootic; prs, presphenoid; ps, parasphenoid ; pt, ptery- 

 goid; ptc, pterygoid cartilage; pto, pterotic; q, quadrate; qj, quadratojugal; r, rostral; rm, 

 rostrum; sa, suprangulare; sbo, suborbital; sc, sagittal crest; scl, sclerotic; se, sphenethmoid; 

 sf, supra temporal fossa; sh, stylo hyal; so, supraoccipital; sop, subopereulare; sor, supra- 

 orbital; sp, sphenoid; spht, sphenoturbinal; spl, splenial; spo, sphenotic; spt, supra temporal; 

 sq, squamosal; ssc, suprascapular; st, stapes; sy, symplectic; /, temporal; tr, 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 



