I02 



VERTEBRATE SKELETON 



transverse row of supratemporals, supracleithra and dermoccipitals 

 crosses the cranium behind. There is a lacrimal (prefrontal?) in 

 front of the orbit; behind the opening is a postorbital or postfrontal, 

 followed by a series of ossicles, one or more of them lateral to the 

 spiracle. The margin of the upper jaw is formed by maxilla and 

 premaxilla, the former followed by the preoperculum. The other 

 opercular bones are an operculare and (except Calamoichthys) a 

 suboperculum. 



The roof of the mouth is lined by vomers and parasphenoid, both 

 tooth-bearing, and a series (ecto-, ento-, and meta-) of pterygoids. 



(.4 ) {B) 



Fig. ioq. — .4. chondrocranium of nearly adult Polypterus with cartilage bones 

 stippled (Biitschli, 'lo); B, adult Polypterus (Wiedersheim, '86). do, dermoccipital; 

 ee, ectethmoid; eo, exoccipital; /, frontal; fh, hypophysial fenestra; m, maxilla; me, 

 mesethmoid; w, nasal; na, naris; nu, nuchal; o, orbit; oo, opisthotic; op, operculare; os, 

 orbitosphenoid; p, parietal; pf, prefrontal; pyn, premaxilla; po, preoperculum (?part 

 postorbital); pof, postfrontal; s, opening of spiracle; sc, supracleithrum; se. supra- 

 ethmoid; so, sphenotic; sop, suboperculum. 



The bones of the lower jaw are dentale, splenial (with a coronoid 

 process), and either angulare or goniale at the angle of the jaw. A 

 labial cartilage (fig. io8) Hes lateral to the jaw behind the coronoid 

 process. A pair of gulars lie between the rami of the jaws; extinct 



