48 ME. E. P. ALLIS OiSr POSTORBITAL ARTICULATION OF 



been quite generally considered to be an otic process ; but if, as I 

 have endeavoured to show, it is the homologue of the processus 

 metapterygoideus of the Teleostomi, this cannot be. Goodrich 

 considers it to be an otic process and says (1909, p. 98) that it 

 " appears to have been established very early, since there is 

 reason to believe that it existed not only in the Jurassic Oestra- 

 ciontidiB (Hyhodics), bvit also in the Oladoselachii, Acanthodii, 

 and Pleurocanthodii." 



In certain of the higher vertebrates a pterygo-ci-anial articu- 

 lation is found between processes which are apparently the strict 

 homologues either of the processus basalis and basipterygoideus 

 of Lspidosteus, or of investing bones related to those processes, 

 the motion between the two processes, however, being a dorso- 

 ventral swinging one instead of a latero-m,esial sliding one. 



In recent Amphibia a cartilaginous processus basipterygoideus 

 seems not to be found (Gaupp, 1900, p. 537), but it is found in 

 certain of the Stegocephali, as explained immediately below. The 

 palatoquadrate of the Amphibia is said by Gaupp to present 

 four typical processes : a processus oticus, processus ascendens, 

 processus pterygoideus, and processus palatobasalis, the latter 

 process being also called by him (1905, p. 736) simply the pro- 

 cessus basalis. In the Urodela, the latter process is said to lie, at 

 first, in contact with the ventral surface of the auditory capsule, 

 at the point where the capsule is connected with the basal plate 

 of the skull, and to later there fuse with it. The process is said 

 to seem to correspond to the palatobasal process of the Selachii, 

 but this seems improbable, for the processus basalis of the 

 Amphibia arises from the pterygoquadrate portion of the palato- 

 quadrate, is directed mesially,and lies against the venti^al surface 

 of the floor of the auditory capsule, while the processus palato- 

 basalis of the Selachii arises from the palatine portion of the 

 palatoquadrate, is directed dorsally, and lies against the orbital 

 wall, which forms part of the lateral surface of the cranium. 



In Hana, of the Anura, the processus basalis is said by Gaupp 

 (1893, p. 349) to first appear in his fourth stage (young frog 

 about 2 cm. long), there arising from the pars metapterygoidea 

 of the quadrate, close above the root of the processus pterygoideus. 

 It is directed toward the ventral surface of the anterior portion 

 of the auditoiy capsule, and an articular joint is Later there 

 formed, this being considered by Gaupp (1905, p. 737) to be a 

 more primitive condition than the fusion of the process with the 

 auditory capsule in the Urodela. In earlier stages of Eana there 

 is a processus muscularis rising from the upper edge of the 

 palatoquadrate, strongly developed in the earliest stage described, 

 but gradually diminishing in importance until its complete 

 disappearance during the metamorphosis. This process lies, in 

 larvae (Gaupp, 1893, p. 292), external to the musculi temporalis 

 and pterygoideus, and gives origin, on its mesial surface, to the 

 masseter, and, on its lateral surface, to the depressor cartila.ginis 

 hyoidece and the depressor mandibulse. The relations of the 



