— 64 — 



In the bony ganoids, as stated above, the process is not found as a part of the quadrate. It 

 is, however, elsewhere represented in both Amia and Lepidosteus. In Amia, it has fused with the 

 symplectic and forms an irregulär articular head of that bone (Allis, 97 a, pl. 20, Fig. 4); while in 

 Lepidosteus it is the preoperculum of Parker's ('82 b) descriptions, and the interoperculum of CoUinge's 

 ('93) descriptions. In Amia the relations are all too evident to leave any doubt as to this homology; 

 and comparison of Lepidosteus with Amia leaves no doubt as to this latter fish. The bone, in Lepi- 

 dosteus, is not properly shown by either Parker or Collinge; the important features omitted being 

 that the bone has an articular head smaller but similar to that in Amia, and that this head articulates 

 with a facet on the posterior surface of a ventrally projecting portion of the articular head of the 

 quadrate. The disappearance of a relatively small intervening wall of quadrate bone, or a slight 

 shifting of the parts together with a concomitant fusion of the bone with the adjoining'symplectic, 

 would produce the conditions found in Amia; while a fusion of the bone with the quadrate, instead 

 of with the symplectic would produce the usual teleostean quadrate. A further fusion of the sym- 

 plectic with the quadrate would apparently produce the conditions found in the Siluridae and those 

 others of the Physostomi in which the process of the quadrate seems absent; thus leaving only the 

 Lophobranchii as apparent exceptions to the general rule. The bone would seem to be, judging from 

 the conditions found in Lepidosteus, a branchiostegal ray related either to the quadrate or to the 

 mandible. 



In Polypterus this process of the quadrate is neither shown nor described, so far as I can 

 determine, and in this fish there is also, according to Traquair ('70), no symplectic. 



It may here be stated that Gymnarchus, in the fusion of the symplectic, the posterior process 

 of the quadrate and the body of the lattef bone into a single piece, and in the intimate and rigid 

 nature of the attachment of the entire suspensoriäl apparatus to the cranium, approaches the 

 amphibian condition, as it does ailso, as I ('04) have lately shown, in the possession of an auditory 

 apparatus resenibling the amphibian ear. 



METAPTEEYGOID. 



The metapterygoid consists of a thick quadrant-shaped endosteal portion, and three thin 

 but extensive flanges that appear to be of purely membrane origin. The curved ventral edge of the 

 quadrant-shaped portion is directed ventro-anteriorly and is everywhere bounded by cartilage, a 

 narrow band of which separates it from the dorsal edge of the quadrate. The angle of the quadrant 

 is directed dorsally, and this angle is apparently the centre of ossification for the endosteal body 

 of the bone and also for the apparently membrane flanges. From this angle a slender process ariscs, 

 and projects dorso-anteriorly in the line prolonged of the bind edge of tTie body of the bone. This 

 process is more than one half as long ias the hind edge of the bone, and has the same general appearance 

 and color as the body of the bone. It may, therefore, also be of endosteal and not of membrane origin. 

 One of the three membrane flanges is a thin web of bone that fills the angle between the anterior 

 edge of this slender process and the dorso-anterior edge of the body of the bone. The other two 

 flanges arise from the füll length of the hind edge of the bone, that hind edge including the slender 

 process as well as the body of the bone. The two flanges project dorso-posteriorly, and, spreading 

 somewhat, enclose between them a V-shaped space. This space lodges and gives insertion to a 

 deeper portion of the levator arcus palatini, the superficial portion of that muscle lying external 

 to the external flange. The V-shaped space also lodges that terminal portion of the external carotid 



