82 



HISTORY OF THE HUMAN BODY 



ally presents an extremely smooth and polished surface which 

 has been often referred to as genuine enamel. Scales of this 



B 



D 



FIG. 19. Dorsal views of various skulls, showing the dermal bones. 



(A) sturgeon (Acipenser). (B) salamander (Amllytfoma). (C) turtle. (D) 

 sea-lion (Otaria). 



ROS, rostral plates; N, nasal; F, frontal; Pr. F, pre- frontal Post. Fr, post-fron- 

 tal; PMX, pre-maxillary; MX, maxillary; J, jugal; QJ ', quadrato-jugal; P, parieialj_ 

 SQ, squamosal; PT, pterygoid; PO, pro-otic; OO, opisth-otic; SO, supra-occipital; 

 Oc. Lot., lateral occipital; OP, opercular; S. Cl., supra-clavicle. 



type, termed ganoid (i. e., shining; from which the Order re- 

 ceives its name), are usually rhomboid in shape and lack the 



