CHONDROCRANIUM OP SYNGNATHUS FUSCUS 441 



nerton, the metapterygoid process of Syngnathus represents a 

 stage in the reduction of an elongate metapterygoid process such 

 as is found in other teleosts. The metapterygoid process does 

 not have the intimate relation with hyomandibula which char- 

 acterizes the metapterygoid process of Salmo and Amiurus. 



As already stated, the symplectic element extends ventral to 

 the anterior margin of the pterygoquadrate and is confluent with 

 it by means of a bridge of cartilage. Continuing posteriorly as a 

 slender cartilaginous core, the symplectic extends mesial to the 

 pterygoquadrate along the entire extent of the latter (figs. 1, 2). 

 A ventral diverticulum of the oral cavity separates it from the 

 copula communis posterior to the pyterygoquadrate. Histo- 

 logically, it has a very heavy perichondrium and there are usually 

 two or three cartilage cells in a cross-section. Posterior to the 

 orbit, the symplectic is connected to the trabecula communis 

 by several strands of embryonic muscle tissue. Finally it 

 becomes confluent with the ventral end of the hyomandibula, 

 no line of division being present between the two. A similar 

 condition is met in the symplectic of Gasterosteus, but as yet 

 the cartilaginous continuity between the distal end of the sym- 

 plectic and the pterygoquadrate characteristic of Syngnathus 

 has not been described. The great distance between the meta- 

 pterygoid process of the pterygoquadrate and the. symplectic 

 is to be noted in Syngnathus as compared to the intimate relation 

 between the elongate metapterygoid and the symplectic in 

 Gasterosteus and Belone (Swinnerton) . 



The hyomandibula at this stage is a rectangular piece of 

 car.tilage which articulates at its dorsal end with the anterior 

 fourth of the otic capsule and is confluent ventrally with the 

 symplectic (fig. 1). Ventromesially, it is flattened for articu- 

 lation with the stylohyal cartilage (fig. 6). The dorsal end of 

 the hyomandibula is thin and rounded where it abuts against 

 the otic capsular wall. The ventral portion is thickened (fig. 6). 

 Near the anterior dorsal margin a small foramen is present for 

 the passage of the ramus hyomandibularis facialis. The abductor 

 hyomandibularis muscle is inserted on the anterior margin of 

 this foramen. The opercular process projects from the posterior 



