270 



LUNG-FISHES 



x. 3- 



A most important feature, common to all crossopterygians, was 

 that the attachment of the jaws was autostylic, that is to say, similar 

 to the arrangement in amphibia and remotely similar to the earliest 

 gnathostomes (aphetohyoids) but different from that of modern elas- 



qj. pop. 



Fig. 161. Skull of Osteolepis. 



d. dentary; en. external nostril; esc. extrascapulars; gu. gular;/. jugal; la. lachrymal; 1-gu. 

 lateral gular; fngu. median gular; mx. maxilla; op. opercular; pa. parietal; pm. premaxilla; 

 po. postorbital; pop. preopercular; ppa. postparietal; prf. prefrontal; qj. quadratojugal; 

 sop. subopercular; sq. squamosal; sut. supratemporal; ta. tabular. (After Save-Soderbergh 

 and Westoll, Biol. Rev. 1943.) 



mobranchs and actinopterygians. The teeth of osteolepids were simple 

 cones, not flattened plates such as are characteristic of Dipnoi, but the 

 teeth on the palate show a somewhat broad folded surface and each 

 tooth is replaced by another growing up near it, both of these being 

 features found in the earliest amphibia. Sections of the teeth show a 

 peculiar infolding of the enamel to make a labyrinthine structure, 

 which is not found in other fishes but is characteristic of the teeth of 

 the first amphibians (p. 327). 



There was only one pair of nostrils on the surface of the head and 

 there are gaps, which are considered to be internal nostrils, at the front 



