The Latero-Sensory Canals and Eelated Bones in Fishes. 455 



tweeii the postfrontal and squamosal (mastoideum) bones; and the 

 supratemporal canal traverses the so-called parietal. This latter fact, 

 so characteristic of tlie Characinidae and Cyprinidae, is of interest 

 because Heterotis is said to possess the beginnings of a Weber's apparatus. 



Anacanthini. 



Gadidae. In Gadus the supraorbital canal is said by Cole [26] 

 to anastomose with the main infraorbital at a bend in the latter 

 canal, between what Cole designates as the "6th. suborbital or 2nd. 

 postorbital ossicle" and the "postfrontal or sphenotic bone". This 

 anastomosis would appear to be by the terminal tube of the supra- 

 orbital line, but it may be that that tube has fused with the penul- 

 timate tube of the same line, the anastomosis thus involving the latter 

 tube also : for there is a tube lacking between organs 4 and 5 supra- 

 orbital that could be as well thus accounted for as by the assumption 

 that it has aborted, or that it is represented by the small blind sac 

 said by Cole (p. 151) to be found partly opposite and partly anterior 

 to organ 4. Tube 4 has fused in the mid-dorsal line with its fellow 

 of the opposite side to form what Cole calls the supraorbital commissure, 

 but the term commissure must not here be taken to imply a cross-commis- 

 sural canal, such as is represented in the ethmoidal and supratemporal 

 commissures of certain fishes, for there are in this commissure of Gadus, 

 as in the corresponding commissure of Lepidosteus, simply two primary 

 tubes, one belonging to the canal of either side of the head, that have 

 met and fused in the mid-dorsal line. 



The infraorbital canal traverses a series of six so-called sub- 

 orbital bones, the 6th. or most posterior of which is also considered 

 by Cole as the 2nd. postorbital bone. This latter bone lodges the 

 tenth sense organ of the line, and this organ is innervated by the 

 second branch of Cole's outer buccal nerve, the first branch of that 

 nerve being the oticus, which innervates organ 11 in the squamosal. 

 Between these two organs. Nos. 10 and 11, the canal comes into 

 relations both with the frontal and the so-called "postfrontal or 

 sphenotic", but it is only partly enclosed in the frontal and simply 

 lies on the dorsal surface of the sphenotic. These two bones thus do 



