CHONDROCRANIUM OF SYNGNATHUS FUSCUS 451 



The mass of cells indicated in the 8-mm. stage as the homologue 

 of the inferior labial cartilage of Gasterosteus has not changed. 

 However, the cells which represented the center of formation of 

 the maxillary ossification have deposited an elongate, vertical 

 lamella. This lamella is connected dorsally with the premaxil- 

 lary lamella anterior to the palatine articulation, and ventrally 

 by a chain of cells with the dorsal tip of the dentary lamella. 

 The maxillary lamella supports the lateral wall of the oral cavity 

 between the end of the cranium and the palatine cartilage. The 

 maxillary lamella bears no teeth. 



The metapterygoid process is longer than it is in the 8-mm. 

 embryo, but even now does not have a relation to the symplectic 

 like that of the larval Gasterosteus. As Swinnerton states, the 

 metapterygoid process of Syngnathus represents a stage in the 

 disappearance of such a structure in the teleosts. The posterior 

 end of this process which in the 8-mm. stage lies posterior to the 

 transverse plane of the ectethmoid cartilages now lies quite 

 far anterior to them (fig. 10). 



The distal end of the symplectic cartilage which in the 8-mm. 

 stage extends the whole length of pterygoquadrate now reaches 

 only to its posterior end. The cartilaginous connection between 

 these two elements has disappeared. The elongation of the 

 symplectic and the subsequent changes in the positional rela- 

 tionships in that part of the visceral apparatus lying anterior 

 to it have already been stated. Ossification has appeared in 

 the form of a curved lamella external to and distinct from the 

 perichondrium of the symplectic shaft. Posteriorly, the proxi- 

 mal end of the symplectic gradually widens as it becomes con- 

 fluent with the hyomandibula, so that the angle, which in the 

 younger stage appears between the proximal end of the sym- 

 plectic and the anterior margin of the hyomandibula, has been 

 obliterated. As a result, it has much the same appearance as 

 that of the 6.6-mm. Gasterosteus. 



The hyomandibula, instead of having the vertical position of 

 the 8-mm. stage, is now directed anteriorly at its ventral end, 

 so that the bulk of the cartilage lies anteroventral to the surface 

 of articulation (fig. 10). The posterior extent of the hyoman- 



