430 



JAMES ERNEST KINDRED 



then it may be stated that the relation cf the ectethmoid carti- 

 lages to the ethmoid plate is more primitive in Syngnathus than 

 in Gasterosteus, where they are never independent. 



The tegmen cranii of the ethmoid region described and figured 

 for Syngnathus peckianus by McMurrich is not present, the 

 brain is enclosed in a fibrous connective-tissue sheath alone 

 (fig. 4). 



pmx. 



brain 



dent. 



Fig 



5-mm. 



Fig, 



3 Cross-section through the anterior end of the ethmoid region of the 

 Syngnathus. Semidiagrammatic. Camera lucida. X 100. 



4 Cross-section through the anterior end of the orbit of an S-mm. Syn- 



gnathus. Semidiagrammatic. Camera lucida. X 100. 



ABBREVIATIONS 



pmx., premaxillary ossification 



pal., palatine cartilage 



ps., parasphenoid ossification 



pt.qu., pterygoquadrate cartilage 



r.c, rostral cartilage 



sym., symplectic cartilage 



trab., trabecula communis 



c.c, copula communis 

 de7it., dentary ossification 

 eth., ethmoid plate 

 int. sept., interorbital septum 

 j.r.p., junction rostropalatinus 

 Mk., Meckel's cartilage 

 o.c, oral cavity 



Posterior to the ectethmoid cartilages, the interorbital septum 

 becomes broader and appears as a meshwork of connective- 

 tissue fibers within which are scattered numerous stellate cells. 

 If we assume with Swinnerton that the ethmoid region ends 

 with the posterior end of the ectethmoid cartilages, then it may 

 be stated that dorsally this meshwork is continuous with the 

 membranous sheath surrounding the brain, and ventrally with 

 the perichondrium of the trabecula communis. 



