438 JAMES ERNEST KINDRED 



As already mentioned, the posterior wall of the otic capsules 

 becomes confluent with the occipital processes and forms a canal 

 on either side of the chondrocranium for the passage of the 

 glossopharyngeal and vagus nerves. 



B. The visceral arches 



The first part of the primordial visceral skeleton to be con- 

 sidered is a small median precranial cartilage, the rostral cartilage 

 (figs. 1, 2, 3). Lying on the middorsal surface of the rostral 

 process of the ethmoid plate, it has a relationship to the latter, 

 comparable to that in other teleosts, as mentioned by Gaupp. 

 This cartilage was not noted by McMurrich in Syngnathus 

 peckianus. Sagemehl ('91), in considering the rostral cartilage 

 in other teleosts, has homologized it to the median synchondrosis 

 which occurs between the distal ends of the palatoquadrate 

 cartilages of Heptanchus. This homology is further borne out 

 by the conditions in Syngnathus at this stage, because the 

 rostral cartilage is connected by densely cellular connective 

 tissue with the anterior ends of the palatine cartilages. The 

 beginnings of the premaxillary ossifications are connected with 

 the lateral surface of this rostral cartilage (fig. 3). It has no 

 homologue in Gasterosteus. 



The anterior ends of the palatine cartilages (ethmopalatines, 

 McMurrich) are flat in cross-section, the mesial surface of each 

 articulates with the lateral surface of the rostral process of the 

 ethmoid cartilage and is connected by fibrous connective tissue 

 with the latter and with the rostral cartilage (figs. 1,3). Poste- 

 rior to the region of articulation, each palatine cartilage tapers 

 and trends ventrally, finally dwindling to a small point embedded 

 in the embryonal connective tissue surrounding the ethmoid 

 plate and the olfactory pit (fig. 1). It is important to note here 

 that the palatine cartilage has a posterior fibrous connection 

 with the dorso-anterior margin of the pterygoquadrate, rather 

 than a cartilaginous connection as in Sahno or Gasterosteus. 

 This condition in Syngnathus bears out the statement made by 

 Swinnerton to the effect that the palatine cartilage does not arise 



