436 JAMES ERNEST KINDRED 



of the notochord is replaced by densely cellular masses of fibrous 

 connective tissue. There are no postvagal nerves in this region 

 and the first neural arch is relatively far distant from the posterior 

 end of the occipital cartilages. 



The postorbital process of the otic capsule appears in the 

 posterior part of the membranous orbital wall (fig. 5), and its 

 anterior end does not extend as far dorsal in the wall as does its 

 homologue in a 6.6-mm. Gasterosteus. In cross-section the 

 postorbital process is very thin and flat, increasing in thickness 

 posteriori}^ At the same time it trends ventrally in the cranial 

 wall (fig. 1). The jugular vein and the gasserian ganglion lie 

 ventral to the postorbital process, and for this reason Swinnerton 

 compared the postorbital process of Gasterosteus to a part of 

 the alisphenoid cartilage of Salmo (Parker, 72) — a comparison 

 with which I am in full agreement as regards the postorbital 

 process of Syngnathus, both from this relation and also from its 

 connection with the otic capsule. 



Posteriorly, the dorsal end of the postorbital process becomes 

 bulbous, the abductor hyomandibularis muscle having its origin 

 on the lateral face. Posterior to the origin of this muscle the 

 dorsal end of the hyomandibula articulates in a groove on the 

 lateral face of the postorbital process (fig. 6). As noted above, 

 the ventral end of the postorbital cartilage becomes the prootic 

 process which trends ventrally and meets the trabecula cranii 

 (figs. 1,2). 



The ramus hyomandibularis facialis and the jugular vein 

 leave the cranium posterior to the prootic process, the dorsal 

 margin of the foramen being formed by the postorbital process 

 (fig. 6). The adductor hyomandibularis muscle has its origin 

 on the ventroposterior margin of this foramen. Similar topo- 

 graphical relationships between the cartilage and the cranial 

 nerves have been described for Gasterosteus, but the muscle 

 relations have not been noted. In a 25-mm. Salmo (Gaupp), 

 a band of cartilage (prafaciale basicapsulare Commissure) con- 

 nects the postorbital process with the parachordal and is perfo- 

 rated by three foramina — an anterior one for the jugular vein, 

 a posterior one for the ramus hyomandibularis facialis, and a 

 ventral one for the ramus palatinus facialis. 



