The Latero-Sensory Canals and Related Bones in Fishes. 405 



stant in fishe8, and the two canals may even always here remain 

 entirely separate. 



The main infraorbital line of Amia is separated, by its manner 

 of innervation, into several portions, an anterior, or ethmoidal com- 

 missural portion, an anterior and a posterior buccal portion, an otic, 

 a glossopharyng-eal, and a vagus portion. The superior postorbital 

 organ is innervated by a nerve that should be probably considered 

 as an anterior branch of the ramus oticus, and it is this organ that 

 becomes enclosed in the so-called dermal postfrontal bone. The next 

 posterior two organs of the line are innervated definitely by the oti- 

 cus. They form the first two organs of the horizontal part of the 

 main infraorbital line, and together with the next posterior organ, 

 which is innervated by the glossopharyngeus, become enclosed in what 

 Sagemehl considered as a purely dermal squamosal. The next poste- 

 rior, or first vagus organ, together with the organs of the correspon- 

 ding half of the supratemporal commissure, become enclosed in the 

 extrascapular; the second vagus organ being enclosed in the supra- 

 scapular, and the third and fourth vagus organs in the supraclavicular. 



The one postfrontal and the two otico-squamosal organs, as they 

 develop, and also as they become enclosed in the main infraorbital 

 canal, form a section of that line and canal that is somewhat inde- 

 pendent of the next adjoining anterior and posterior sections. This 

 section of canal, which may be called the squamoso-postfrontal sec- 

 tion, bends, between its squamosal and postfrontal portions, abruptly 

 downward at the hind margin of the eye, and the primary tube formed 

 at the bend is the one that anastomoses with the penultimate tube 

 of the supraorbital line. 



At the primary tube that lies between the posterior otic organ 

 and the glossopharyngeal organ, the main infraorbital canal anasto- 

 moses with the preoperculo-mandibular canal. 



The organ lodged in the so-called dermal postfrontal bone is, in 

 position, as I have just above stated, the dorsal postorbital organ of 

 the main infraorbital canal; and the purely dermal bone that encloses 

 this organ must be carefully distinguished from the bone generally 

 known and described in fishes as the postfrontal, which latter bone 



