THE GANOIDEI. 



141 



In the Sturgeon (Fig. 40), the membrane bones of the 

 roof of the skuU are more numerous and distinct than in 

 Spatularia, and large dermal bones (J, K, L) are united 

 with them, to form the great cephalic shield. The suspen- 



Fig. 40. 



Fijr. -10. — The cartilaginous skull of a Sturgeon, with the cranial bones. 

 The former is shaded, and supposed to be seen through the latter, 

 which are left unshaded:— a, ridge formed by the spinous processes 

 of the anterior vertebrae ; b, b, lateral winglike processes ; c, rostrum ; 

 Av, position of the auditory organ ; Na, position of the nasal sacs ; 

 Or, that of orbit. The membrane bones of the upper surface are : A, 

 the analogue of the supra-occipital ; B, B, of the epiotics ; E, of the 

 ethmoid ; G, G, of the postfrontals ; H, H, of the prefrontals ; C,C, 

 the parietals ; IJ, I) are the frontals, and F, F the squamosals ; K, 

 the anterior dermal scute : /, I and L. L. dermal ossificatioas con- 

 necting the pectoral arch with the skull. 



Fig. 41. 



Fig. 41 . — Side-view of the cartilaginous cranium oi Accipenser : —a, ros- 

 trum ; b, nasal chamber ; Or, orbit ; c, auditory region ; d, coa- 

 lesced anterior vertebrae ; e, ribs ; /, (/, h, suspensorium ; k, palato- 

 maxillary apparatus; ilf«, mandible. 



sorium ( f, g, h, Fig. 41) is divided into two portions, to the 

 lower of which (at h) the proper hyoid is attached ; and the 

 palato-quadrate cartilages, with their subsidiary ossifications. 



