CHONDROCRANIUM OF SYNGNATHUS FUSCUS 455 



2. The presence of a definitive fenestra myodomus ventralis 

 between the anterior ends of the trabeculae cranii. 



3. The absence of cartilage on the dorsal and ventral surfaces 

 of the intercranial notochord. 



4. The presence of a taenia tectum medialis in the cranial 

 roof. 



5. The presence of a minute basicapsular fenestra in the ventral 

 wall of each otic capsule. 



6. The fibrous connection between the posterior end of the 

 palatine cartilage and the dorsal end of the pterygoquadrate 

 cartilage. 



7. The presence of an elongate symplectic cartilage and a 

 slender hyomandibula. 



8. The great length of the trabecula communis and the ethmoid 

 plate. 



9. The change in position of the hyoid elements during 

 development. 



10. The presence of a reduced metapterygoid process. 



The chondrocranial characters of Syngnathus which may be 

 regarded as primitive are : 



1. The presence of a rostral cartilage which has been con- 

 sidered by Sagemehl in other teleosts as the homologue of the 

 median synchondrosis between the palatopterygoid cartilages 

 of Heptanchus. 



2. The development of the ectethmoid cartilages independ- 

 ently of the ethmoid plate, which seems to the author to indicate 

 that they are the remnants of an olfactory capsule which devel- 

 oped independently. 



3. The open communication between the cavum labyrinthii 

 and the cavum cranii. 



4. The absence of postvagal nerves in the occipital region. 

 From the above preponderance of specialized characters, it 



may be concluded that even in its early stages of development 

 the skull of Syngnathus is already highly specialized. 



