— 181 — 



others branch repeatedly, fonaing complicated dendritic Systems. The tubules are scattered along 

 the cana] instead of being grouped together, and it is impossible from the tubules alone to determine 

 the number of primary tubes. Furthermore, here, as in other parts of the latero-sensory System 

 of this fish, the hirge dendritic Systems arise from the canals in the bodies of the related bones, 

 frequently near tlie middle point of the bone, and almost never in the sutural line between two 

 bones; tbis being distinctly a characteristic of the canals in the chondrostean ganoids, here found 

 in a teleostean fish. A füll knowledge of the development of the system woidd accordingly be of 

 considerable interest. 



The main infraorbital canal, having left the dorsal one of the infraorbital bones, enters and 

 traverses the postfrontal, at the dorsal end of which bone it turns sharply backward and enters the 

 pterotic, anastomosing at the bend with what appears to be the terminal tube of the supraorbital 

 canal. The main infraorbital then traverses in succession the pterotic and suprascapular, lying for 

 a short distance, as it passes from one of these bones to the other, in a groove on the lateral edge 

 of the lateral extrascapular. It then traverses a short tubulär bone that lies along the lateral edge 

 of the suprascapular and that apparently represents the latero-sensory component of the supraclav- 

 icular, as already set forth. As the canal traverses the pterotic it anastomoses with the dorsal 

 end of the preopercular canal, and as it traverses the lateral edge of the lateral extrascapular, it 

 gives off the supratemporal commissure. 



In the main infraorbital canal there are three sense organs lodged in the lachrymal, two in the 

 second infraorbital bone, three in the third infraorbital and one in the fourth infraorbital, all inner- 

 vated by the ramus buccalis. In the postfrontal there is one organ innervated by the ramus oticus, 

 and in the pterotic three organs, two innervated by the oticus and one by the supratemporalis lateralis 

 vagi. In the section of canal that lies in the groove in the lateral extrascapular there is apparently 

 no organ, but the organ usually found here raay be represented in a part of the one organ found in this 

 bone. This organ is unusually large, begins in the main canal, and from there extends postero- 

 mesially in the supratemporal commissure, thus certainly belonging, in part at least, to that commis- 

 sure. It is innervated by a single branch of the supratemporalis lateralis vagi. In the supra- 

 scapular there is one organ, innervated by the supratemporalis lateralis vagi. 



The supratemporal canal begins at the lateral edge of the lateral extrascapular, opposite the 

 sutural line between the pterotic and suprascapular, and running postero-mesially and then mesially 

 traverses the lateral extrascapular and then the mesial extrascapular, anastomosing, at the mesial 

 edge of the latter bone, with its fellow of the opposite side. Each of these two bones lodges a single 

 sense organ innervated by a branch of the supratemporalis lateralis vagi. 



The supraorbital canal begins at the lateral edge of the single median nasal bone, and from 

 there runs upward and mesially, and then upward and backward in the nasal, curving around the 

 anterior and then the mesial border of the large nasal opening of the skull. It then enters the anterior 

 edge of the frontal and runs almost directly backward to the middle point of that bone. There it 

 turns sharply laterally, and then curving laterally and backward reaches the postero-lateral edge of 

 the frontal, where it anastomoses, by what is apparently its terminal tube, with the main infraorbital 

 canal. In the füll length of the canal there are, as in all the other fishes of the group, six sense 

 Organs, one in the nasal and five in the frontal, all innervated by the ophthalmicus lateralis; but in 

 Dactylopterus the relations of the organs in the frontal to the frontal commissure are not as in those 

 other fishes. Here, three organs lie anterior to the commissure and two posterior to it, the commissure 



