CHONDROCRANIUM OF SYNGNATHUS FUSCUS 429 



posteriorly with the trabecula communis which forms the axis 

 of the orbital region. The interorbital septum of loose strands 

 of fibrous connective tissue is directly continuous with the 

 perichondrium of the ethmoid plate (fig. 4). The olfactory pits 

 lie lateral to the interorbital septum and are embedded in embry- 

 onal connective tissue. 



Just posterior to the olfactory pits and ventral to the anterior 

 end of the brain there is a pair of cartilaginous rods. These 

 extend ventrolaterally from the membranous tissue enclosing the 

 brain into the embryonal connective tissue lying in the anterior 

 portion of the orbit (fig. 1). McMurrich, in describing the 

 chondrocranium of a 6- to 7-mm. Syngnathus peckianus, inter- 

 preted these as the nasal cartilages. In other teleosts the ecteth- 

 moid cartilages occur in this region as lateral outgrowths 

 from the ethmoid plate. In later stages of Syngnathus the 

 ectethmoid processes are completely fused with the ethmoid 

 plate, the whole forming a mesial internasal septum. Hence 

 from their position and their later history these independent 

 cartilages are to be regarded as ectethmoid cartilages, but at 

 the same time this condition indicates that the ectethmoid 

 cartilages were derived phylogenetically from the posterior wall 

 of the cartilaginous olfactory capsules and that only a remnant 

 of these is left in Syngnathus. If this point of view is accepted, 



ABBREVIATIONS 



br.I-IV, branchial arches I to IV Mk., Meckel's cartilage 



c.c, copula communis mpt.pr., metapterygoid process 



ct.h., cerato hyal occ.pr., occipital process 



ect., ectethmoid cartilage ot.c, otic capsule 



eth., ethmoid plate pal., palatine cartilage 



f.bcr.p., fenestra basicranii posterius pch., parachordal 



f.hyp., fenestra hypophyseos po.pr., postorbital process 



f.my.vent., fenestra myodomus ven- pr.po., prootic process 



tralis pt.qu., pterygoquadrate cartilage 



f.m., foramen magnum r.c, rostral cartilage 



J. VII, foramen for ramus hyomandib- rs.p., rostral process of ethmoid 



ularis facialis styl.h., stylohyal cartilage 



Hyom. VII, foramen in hyomandibula sym., symplectic cartilage 



for r.hyom.fac. taen.tect.med., taenia tectum medialis 



hyp.h., hypohyal trab.comm., trabecula communis 



j.r.p., junction rostropalatinus trab.cr., trabecula cranii 



