132 Edward Phelps Allis jr., 



nearly a right angle, and enters and traverses two postorbitals and 

 a postfrontal, between each two of which three bones there is an en- 

 largement of the canal which represents a blind and aborted primary- 

 tube. At the dorsal end of the postfrontal the canal turns sharply 

 backward, anastomosing at the bend with the hind end of the supra- 

 orbital canal, and enters a canal, in the skull, from which it issues on 

 the dorsal surface of the skull, near its hind end. It then traverses 

 a short tubular ossicle, and on leaving it opens into the transverse 

 canal formed by the end-to-end anastomosis of the supratemporal and 

 preoperculo-mandibular canals. 



The infraorbital canal of Myrus thus agrees exactly with that of 

 Ophicthys excepting that the two postorbital primary tubes are blind, 

 that the anterior suborbital bone has not fused with the lachrymal, 

 and that a primary tube is retained, instead of being aborted, between 

 the first two organs of the line. 



The ethmoidal canal begins at a pore that lies on the ventral 

 surface of the anterior end of the snout, slightly anterior to the nasal 

 tube. From there it runs upward and backward into a central cavity 

 in the anterior end of the skull, and then turns forward to anastomose by 

 its hind end with the anterior end of the supraorbital canal. The 

 double primary tube resulting from this anastomosis opens on the 

 outer surface by a pore that lies dorso-mesial to the anterior edge of 

 the nasal tube. 



The supraorbital canal, beginning at the above mentioned double 

 pore, runs backward into the nasal bone, which it traverses, giving 

 off, as it traverses it, one primary tube and pore. At the hind end 

 of the nasal, which end lies at a point dorso-mesial to the middle 

 point of the eye, the canal leaves the nasal and enters a canal in the 

 fused bones of the skull, a swelling of the canal here indicating an 

 aborted primary tube. At the level of the hind edge of the eye the 

 canal turns latero - postero - ventrally and anastomoses with the main 

 infraorbital, a primary tube being given off: at the bend. This latter 

 tube, as in Ophicthys, runs postero-mesially and fuses, in the middle 

 line, with its fellow of the opposite side, but the pore that should 

 normally here be found is closed. 



