m 



Me. C. tAtE RfiGAK ON THE 



frontals are normally developed. Anteriorly there is a small 

 dermal ethmoid, and paired nasals and adnasals cover the 

 olfactory sacs, Avhich lie in concavities of the prpemaxillaries, 

 above the dentigerous margin of the latter. The prsemaxillaries 

 run backwards to below the frontals, expanding on the upp'ei^ 

 surface of the snout to form a pair of rugose plates (ethmo-nasals 



Text-fiffure 1, 



pi'o^J 



A. 



B. 



Upper surface of skull of A, Ijepidosteus tristoechus ; and B, L. osseus. 

 Lettering as in text-fig. 2. 



of Parker) ; below this they form a pair of thick-walled tubes 

 that carry the olfactory nerves ; they embrace the slender 

 anterior portion of the rostral cartilage and are attached below 

 to the vomers and parasphenoid (text-fig. 3). 



The vomers are laminar bones attached to the lower surface 

 of the parasphenoid and prsemaxillaries ; each sends Lack a long 



