412 Edward Phelps Allis jr., 



the ethmoidal canal anastomoses, apparently by its terminal tube, with 

 the penultimate tube of the suborbital part of the main infraorbital 

 canal, exactly as it did in the one larva that was sectioned; and in 

 addition to this anastomosis it also anastomoses, apparently by its own 

 penultimate tube, with the anterior end of the supraorbital canal, 

 this latter anastomosis not yet having been acquired in larvae. In 

 the ethmoid bone two tubes arise from the canal in addition to the 

 median tube. The next following-, or fourth tube arises from the canal 

 as it passes from the ethmoid into the antorbital; and the fifth tube 

 soon after entering* the latter bone. By what is apparently its sixth 

 tube the canal anastomoses with the supraorbital canal, and by its 

 seventh or terminal tube with the penultimate tube of the suborbital 

 part of the main infraorbital. A foramen, doubtless for the passage 

 of a nerve, is found in the canal between each two of these tubes, 

 and quite undoubtedly indicates the position of a sense organ, the 

 number of organs thus agreeing with that found in the larva. 



The suborbital section of the main infraorbital canal begins 

 immediately posterior to the posterior nasal aperture, at the dorsal 

 edge of the antorbital bone, and has there anastomosed with that 

 tube of the supraorbital canal that arises from that canal as it passes 

 from the nasal bone into the ethmo-nasal of Parker's and Collinge's 

 descriptions. This anastomosis takes place, in Lepidosteus, posterior 

 to the posterior nasal aperture, while, in Amia, what is apparently 

 the corresponding anastomosis takes place anterior to that aperture; 

 but this anastomosis in Amia is a secondary and not a primary one 

 [5, p. 476]. Starting from this point, the canal, in Lepidosteus, runs 

 almost directly laterally and downward until it meets and anastomoses 

 with the hind end of the ethmoidal canal. It then turns backward, 

 practically at a right angle, ti-averses the posterior portion of the 

 antorbital bone, and then enters the anterior one of the chain of 

 so-called maxillary ossicles. It here turns postero-mesially along the 

 anterior edge of this first bone of the chain, passing antero-mesial to 

 a large foramen in the bone which gives passage to the point of the 

 second mandibular tooth. A similar perforation of the completely 

 fused so-called premaxillary and ethmo-nasal bones, for the passage 



