436 * Edward Phelps Allis jr., 



then backward in the parietal until it reaches the anterior edge of 

 the supratemporal canal, where it comes to the surface and ends in 

 a single pore. The nasal lodges one sense organ of the line, the 

 frontal four. A primary tube leaves the canal between each two 

 successive organs and they all open on the outer surface by a single 

 pore excepting only the fourth tube, which has undergone division 

 and opens by two pores. The fifth, or penultimate tube runs laterally 

 and backward to the lateral edge of the frontal and there fuses with 

 the tenth infraorbital tube, which latter tube is given oft" as the infra- 

 orbital canal passes from the postfrontal into the squamosal. 



The supratemporal canal leaves the main infraorbital canal in 

 the extrascapular, runs mesially and forward through the latter bone, 

 mesially and then mesially and backward through the so-called parietal, 

 and at the mesial edge of the latter bone unites with its fellow of 

 the opposite side. The extrascapular lodges one sense organ of the 

 canal, and the so-called parietal a second organ. The mesial one of 

 two mesial extrascapular bones is thus here fused with the parietal, 

 the lateral one of the two mesial extrascapulars being fused with the 

 lateral extrascapular. 



The preoperculo-mandibular canal is shown in the figures, and 

 needs no special description in this connection. 



Alestes nurse. The canals in Alestes are shown in figs. 15 and 

 16. They agree so closely with those in Hydrocyon that no detailed 

 description of them is needed. Tubes 7 and 8 infraorbital are peculiar 

 in that they extend backward so far that they overlap the preoper- 

 cular canal, tube 8 overlapping the latter canal but slightly, but tube 7 

 extending a considerable distance beyond it on to the outer surface 

 of the operculum. Tube 8 seemed to communicate directly with the 

 preopercular canal, though this could not be positively established, 

 thus here producing what might appear as, and might easily be 

 mistaken for, a commissural line connecting the two main canals. 

 The dorsal preopercular tube, like tube 7 infraorbital, extends back- 

 ward a considerable distance on the outer surface of the operculum, 

 and both of these tubes might easily be mistaken for branch canals. 



On the left side of the head the fourtli supraorbital organ was 



