444 Edward Phelps Allis jr., 



infraorbital canal as that canal passes on to the anterior edge of the 

 squamosal. At the point where it turns laterally to join the main 

 infraorbital, a primary tube is sent directly backward, in the line of, 

 and as a direct continuation of the canal anterior to that point, this 

 being the only tube that could be found in this canal. There was, 

 in the specimen used for illustration, one sense organ in the canal 

 posterior to the point of origin of this tube, and ten anterior to it. 

 The anterior four organs were found in that part of the canal that 

 lies in the groove in the nasal bone, and the remaining organs all in 

 relation to the frontal, as shown in the figure 



The main infraorbital canal begins at the anterior end of the 

 lateral edge of the "Nasenmuschel" (bone No. 4) of Erdl's descriptions, 

 there lying in an open groove on the thickened lateral edge of that 

 bone. At about one half, or two-thirds the length of this bone, the 

 canal passes into a groove on the anterior one of the orbital bones 

 (bone 32) of Erdl's descriptions, this bone being attached to the 

 lateral edge of the posterior portion of the Nasenmuschel (bone 4). 

 Beyond this first orbital bone the canal continues backward traversing 

 a groove in each succeeding orbital bone until it reaches the most 

 posterior bone of the chain, in which bone it may either still lie in 

 an open groove, or become entirely enclosed in the bone by the for- 

 mation of a very delicate roof above the groove. Beyond this latter 

 bone the canal enters a groove on the outer surface of the squamo- 

 sal, and there immediately anastomoses with the terminal tube of the 

 supraorbital line. It then turns downward and backward, at a sharp 

 angle, and so continues until it meets and anastomoses with the dorsal 

 end of the preopercular canal, lying, in this part of its course, in a 

 large groove on the outer surface of the curved inferior arm of the 

 squamosal; which groove is probably the "Knochenkanal" of Erdl's 

 descriptions. 



Posterior to the preopercular canal the main infraorbital canal 

 has a curved course, lying, at first, on the dorsal surface of the in- 

 ferior arm of the squamosal, that bone not here being grooved, and 

 then in the tissues immediately external to the postero-lateral edge 

 of a part of bone 14 of Erdl's descriptions, that bone certainly being 



