70 



ALUS. [Vol. XVIII. 



much more to an antorbital than to an ethmoid, and its fibrous 

 connection with the maxillary and premaxillary, lateral to the 

 ascending process of the latter bone, are certainly in conformity 

 with the conditions found in Amia, the ascending process of the 

 premaxillary of Scomber being considered as the homologue of 

 the ethmoid of Amia (No. 7) . The nasal bone of Scomber would, 

 in that case, be more properly called an antorbito-nasal. 



In Amiunis, McMurrich describes an adnasal bone (No. 48, 

 p. 278). He says of it that it is an anterior continuation of the 

 infraorbital chain of bones, and is traversed by the main infra- 

 orbital canal ; but the name given to it indicates that it must have 

 closer relations to the nasal bone than to the infraorbital ones. 

 It is said by CoUinge (No. 19, p. 280) to be called by some 

 authors the antorbital. It may represent a condition in the fusion 

 of the antorbital with the nasal that is intermediate between the 

 conditions found in Amia and those in Scomber. 



The Frontals {FR) occupy more than three fifths of the full 

 length of the dorsal surface of the skull, and form by far the 

 larger part of that surface. In the posterior half of their length 

 they are connected with each other by suture in the middle line 

 of the head. In their anterior halves they diverge slightly from 

 each other, and there disclose a small triangular bit of the chondro- 

 cranium and the median portion of the posterior half of the dorsal 

 surface of the ethmoid. The extreme anterior end of each frontal 

 usually turns slightly outward, and it there rests upon the posterior 

 edge of the corresponding dorso-lateral process of the ethmoid. 



Proceeding backward from the anterior end of the bone, the 

 frontal widens gradually, with a wavy and irregular lateral edge, 

 until it reaches the postorbital ossification, where it attains its 

 greatest width. Posterior to this point the line of the lateral edge 

 of the frontal is continued by the dorso-lateral edge of the post- 

 orbital ossification, the frontal seeming to have its entire postero- 

 lateral corner cut away at a sharp and varying angle. The frontal 

 here lies directly upon the postorbital ossification and a part of the 

 latter bone seems to have here reached the dorsal surface of the 

 skull by the wearing away, figuratively, of the frontal by the over- 

 lying dilatator operculi muscle. 



