130 Edward Phelps Allis jr., 



main infraorbital as that canal bends backward on leaAdng the dorsal 

 end of the postfrontal bone. The larger part of this supraorbital 

 canal is enclosed in the nasal, that bone extending from immediately 

 posterior to the double etlimoid-supraorbital piimary tube back to a 

 point dorso-mesial and slightly posterior to the centre of the eye. 

 The anterior and posterior ends of the nasal are long, narrow, and 

 somewhat cylind^'cal, its middle part expanding latero-ventrally so that 

 it covers the nasal sac but not the posterior nasal passage. Two 

 primary tubes leave the canal as it traverses the bone, one opening 

 by a pore that lies dorso-mesial and slightly posterior to the anterior 

 nasal aperture, and the other by a pore that lies in the transverse 

 plane of the posterior nasal aperture. Another tube, the fourth of 

 the line, leaves the canal at the hind end of the nasal. The nasal 

 thus quite certainly lodges three sense organs of the supraorbital line, 

 one of them lying in the long and unusual posterior extension of the 

 bone. This seems to indicate that a lateral sensory ossicle that would 

 usually form part of the frontal, and that may represent a separate 

 prefontal bone, has, in this fish, fused with two true nasal ossicles. 



On leaving the nasal at its hind end the supraorbital canal im- 

 mediately enters a canal in the bones that here form the skull of the 

 fish and that are so completely fused that their limits even cannot be 

 definitely determined. The canal here runs backward a certain distance 

 in the skull and then turns latero-ventro-posteriorly and anastomoses 

 with the niain infraorbital, as already stated. In the short section 

 of supraorbital canal here enclosed in the skull there are two sense 

 organs, and it is thus evident that the bone that immediately surrounds 

 the canal must be the frontal. Between these two frontal organs, at 

 the bend in the supraorbital canal, a primary tube arises. Running 

 postero-mesially, it anastomoses, in the middle line, with its fellow of 

 the opposite side, the two tubes opening by a common and single 

 median pore. 



The supratemporal canal is a complete cross-commissure and is 

 enclosed, on each side, in two tubular ossicles. Between these two 

 ossicles, on each side, there is a primary tube and pore; as there is 

 also in the middle line between the ossicles of opposite sides. At its 



