Nos. IAND2.] ANATOMY OF SCOMBER SCOMBER. 255 



thus definitely includes the postf rental organ of the line. In Amia 

 the postfrontal organ, although innervated by a branch of the buc- 

 calis that is relatively separate and distinct from the ramus oticus, 

 is enclosed in its canal before the adjoining organ, No. 13, and is 

 enclosed independently of that organ (No. 2). It accordingly 

 belongs, in its development, as the corresponding organ in Scoi>i- 

 ber does in its innervation, much more to the otic part of the main 

 infraorbital canal than to its buccal portion, and it may represent, 

 as alread}' stated, the anterior organ of a morphologically separate 

 part of the line. If so the arrangement shown by Pollard in 

 Trichomycterus (No. 59, Fig. 5) would be naturally explained. 

 In Menidia the ramus oticus facialis is even said to innervate two 

 postorbital organs (No. 36, p. 429). 



In Aiuia the oticus facialis traverses a canal that lies between the 

 postorbital ossification and the adjoining cartilage of the chondro- 

 cranium, and, on issuing on the dorsal surface of the skull, it 

 passes directly to the organs it innervates, sending its first branch 

 to the spiracular sense organ. In Scomber the nerve, after having 

 first passed into the orbit, traverses a canal that lies wholly in the 

 postorbital ossification ; and those two branches of the nerve 

 that supply the two squamosal organs take what seems a most 

 indirect and circuitous course to reach their destination. This is 

 due to the fact, already mentioned, that the dilatator operculi, in 

 acquiring its origin on the dorsal surface of the skull, has crowded 

 the nerve away from the canal that it innervates. The nerves do 

 not cut into or through the muscle, but cross its outer surface, and 

 then turn inward beyond it to reach the canal they supply. The 

 fact that the muscle thus passes forward mesial to the canal trav- 

 ersed by the trunk of the nerve, and the further fact that that 

 canal is much larger than is necessary simply for the passage of 

 the nerve, would seem to indicate that the canal is in part a rudi- 

 ment of the spiracular canal of Amia. 



The second branch of the buccalis of Scomber innervates organ 

 9 infraorbital. 



The third branch is given ofif after the buccalis has received 

 the first small anastomosing branch from the truncus maxillaris 

 trigemini, and just before it has its first important anastomosis 

 with the maxillaris superior. It separates into three branches and 

 innervates organs 8. 7 and 6 infraorbital. 



