106 EDWARD PHELPS ALFJfs, JUN. 



head. There it lies latero-ventral to the anterior, united ends 

 of the dorso-lateral and ventro-mesial rostral cartilaginous 

 bars of the skull. 



At this point the canal turns backward, and here lies lateral 

 to the dorso-lateral rostral bar of cartilage, lying, however, 

 at such a considerable distance from it that the bar would 

 seem to have no direct supporting relation to the canal. The 

 canal, moreover, here lies latero-superficial to the bar, and 

 not directly superficial to it. 



When the canal, in its backward course, now reaches the 

 transverse plane of the anterior end of the nasal capsule, it 

 approaches the roof (morphologically floor) of the capsule, 

 and here sinks to such an extent below the external surface 

 of the head that, when it curves forward, in front of the eye, 

 the dorsal arm of the bend lies at first directly dorsal to the 

 ventral one, at a normal distance from the surface. After 

 the canal has again turned backward it soon comes to lie 

 directly superficial to the rounded dorso-lateral surface of the 

 neighbouring part of the skull, and continuing backward 

 passes on to the dorsal surface of the projecting cartilaginous 

 roof of the orbit. 



There were in all, in the entire length of the supra-orbital 

 canal, 93 sense organs. The number of tubules leading from 

 the canal was much larger, many of them having undergone 

 subdivision. In certain parts of the line they were, however, 

 still found, one tubule between each two successive organs. 

 Directly on the top of the snout, about midway between the 

 anterior end of the snout and the point where the canal takes 

 its double bend in front of the eye, there was a large and com- 

 plicated group of tubules. These tubules all issued from the 

 canal on its mesial side, and ran mesially or mesially and 

 backward. At a varying but short distance from their bases 

 they were all connected by short communicating branches, 

 these branches together having somewhat the appearance of 

 a single curved connecting canal. Beyond these communi- 

 cating branches certain of the tubules branched dichoto- 

 mously in the plane of the ectoderm. In the plane per- 



