OSTEOLOGY, ETC., OP SYNGNATHUS PECKIANTJS. 637 



cartilage which articulates with the mandibular^ shows con- 

 clusively that it can be no other than the pterygo-quadrate. 



Other discrepancies between Ryder's paper and my own, 

 such as the transverse segmentation of the hyomandibulai* 

 arch, the existence of a distinct symplectic (which probably is 

 my geniohyal), and the division of the hyoid element into 

 cerato- and hypohyal portions, will be noticed at once on com- 

 parison, and certain of them may be due to the difference in 

 the age of the forms compared. 



Adult. — I must here repeat the statement made previously 

 that intermediate stages between d and the adult were not 

 obtained. As a consequence some of the points in the follow- 

 ing description are merely conjectures. There is a certain 

 amount of complication, owing to the excessive elongation of 

 the symplectic, and the presence of membrane bones, which 

 study of the intermediate stages can alone satisfactorily 

 unravel. 



The hyomandibular articulates with the skull immedi- 

 ately behind the orbit, the articular surface being afforded it 

 apparently by the sphenotic, pro-otic, and pterotic. Its direc- 

 tion is perpendicular to the longitudinal axis of the skull, and 

 it is composed of a central cartilage surrounded by ectosteal 

 bone (fig. 10, H. M.). 



Below it articulates with the interhyal (I. H.), a some- 

 what triangular ossicle, in which the original cartilage still 

 persists. This forms the connecting link between the hyo- 

 mandibular and hyoid element proper. The latter (Hy.) 

 consists apparently of two portions, a cerato- and hypohyal, 

 the epihyal being apparently absent. The elements of either 

 side approach each other in the median line below, and are 

 moveable upon the interhyal. Two muscles, inserted by a 

 single tendon, pass from their distal extremities backwards, 

 and anteriorly they are connected with the mandible. AVhen 

 the muscle is in a state of repose the hyoids are bent up on 

 the under surface of the skull, and lie between the symplec- 

 tics ; by its contraction their extremities are drawn downwards, 

 and consequent upon this there is a similar downward move- 



