MORPHOLOGY OF TELEOSTEAN HEAD SKELETON. 545 



regarded as an articular surface. Its total disappearance 

 in older individuals also tells strongly against tliis view. 



The ossification of the quadrate, which commenced around 

 the articular head, has now extended over a considerable 

 portion of the main body. From its lower edge, and jusb 

 behind the articulation, the bone sends out a long process- 

 like extension, triradiate in cross-section, and half the length 

 of the quadrate. 



The metapterygoid process {qu. m.) still maintains its 

 relationship to the symplectic, and its extremity has become 

 the metapterygoid bone. Owing to the extension of bone 

 far beyond the end of the cartilage the process now seems 

 to end some distance above the level of the stylohyal, as 

 in the salmon ; therefore this feature, being secoudaiy, is not 

 important. 



The palatine bone {pa.), unlike the metapterygoid, is not 

 at the end of the process, but around it, and mainly behind 

 its attachment to the ethmoid. The process (fig. 9) is, rela- 

 tively, much slenderer than at any previous stage, and its 

 extremity, owing to the continued growth of the maxillary pro- 

 cess (figs. 9, 13, jjct. 1)1.), is expanded. Behind this the cartilage 

 is not merely in contact, but in actual continuity with that of 

 the pre-ethmoid cornu (fig. 30, e.pr.). The palatine bone sur- 

 rounds this point, and extends back almost to the level of the 

 parethmoid. For a short distance, about the middle of its 

 leugth, this bone has completely replaced the enclosed 

 cartilage (as indicated by the yellow in fig. 9, |)o.). Thus at 

 this stage the cartilage of the palatine process becomes 

 broken into an anterior portion, having the same relationships 

 as the " ethrao-palatine " of Syngnathus or Siphouostoma 

 (fig. 48, pa.) ; and a hinder portion, widely separated from 

 this and continuous posteriorly with the quadrate cartilage, 

 and therefore homologous with the " pterygoid process " of 

 these forms. It is quite conceivable, therefore, that in these 

 highly specialised forms, the ontogenetic stage, having the 

 " ethmo-palatine " continuous Avith the " pterygoid process " 

 (as, for example, that shown in Stage III, fig. 8, qu. pa., of 



