462 Edward Phelps Allis jr., 



traverses the nasal, giving off, usually near the hind end of the bone, 

 the trunk of a dendritic sj'steni, this trunk and also the anterior terminal 

 trunk both branching repeatedly. Posterior to the second trunk there 

 is a sense organ in the nasal, and then another branching trunk is 

 given off by the canal as it passes from the nasal into the frontal. 

 The trunk that is given off as the canal traverses the nasal is thus 

 simply one half of the anterior terminal primary tube of the canal, 

 the trunk given off between the nasal and frontal being the second 

 primary tube of the line. Having entered the frontal the canal tra- 

 verses that bone until it arrives at the hind edge of the orbit, where 

 it turns laterally, and almost immediately joins and anastomoses with 

 the main infraorbital, as or slightly after that canal passes from the 

 postfrontal into the frontal. As the canal here turns laterally it 

 gives off, on its mesial aspect, a long primary tube, the 3rd. of the 

 line. This third tube takes a curved course at first mesially and 

 downward, and then almost directly upward, or even upward and 

 laterally, and joins, in the suturai line between the two frontals, a 

 corresponding tube from the other side. Close to and slightly posterior 

 to this 3rd. tube, another tube, the 4th. of the line, is sent upward 

 and backward to the outer surface of the frontal; and shortly beyond 

 this latter tube the canal anastomoses with the main infraorbital, no 

 tube arising from the canal at the point of anastomosis. Between the 

 3rd. and 4th. tubes there is a sense organ in the canal, another 

 organ being found slightly anterior to the 3rd. tube. And these two 

 organs and the one organ in the nasal are the only organs that could 

 be found in the canal. As no organ is found between the fourth tube 

 and the point where the canal anastomoses with the main infraorbital, 

 it is evident that this fourth supraorbital tube, and that tube that arises 

 from the main infraorbital in the dorsal portion of the postfrontal 

 bone, together represent the double tube primarily formed where the 

 two canals anastomose. These two tubes are, therefore, each half tubes. 

 The left supraorbital canal begins, as the right one does, at the 

 anterior end of the nasal bone of its side; but after traversing that 

 bone, it perforates, as Traquair states, the ethmoid (nasal, Traquair) 

 before entering the anterior end of the frontal of its side. A primaiy 



