The Latei'o-Sensory Canals and Related Bones in Fishes. 481 



of the specimen figured, a series of sixteen ossicles, the anterior ones 

 of which are tubular while the posterior ones are somewhat flattened, 

 as shown in figure 39. In these latter ossicles, the canal lies in an 

 open groove, instead of being, as in the more anterior ossicles, wholly 

 enclosed. All of the ossicles are firmly and closely attached, by 

 connective tissue, to the ventral surface of the cartilaginous rostrum, 

 and a primary tube leaves the canal either between each two of the 

 ossicles, or partly enclosed in one of them, an additional tubule leaving 

 the canal near the middle of certain of the ossicles. So far as could 

 be determined there was a sense organ in the canal opposite, or nearly 

 opposite each tubule, the organ always lying in one of the ossicles, 

 and not between them. Having entered the lower postorbital bone the 

 canal soon turns upward, in it, here passing from the ventral surface 

 of the head onto its lateral surface. It then runs directly upward be- 

 hind the eye, through the lower and then through the upper post- 

 orbital bones, then turns backward and upward in the postfrontal bone 

 of Huxley's and Gegenbaur's descriptions, and having traversed that 

 bone enters the squamosal where it soon anastomoses with the hind 

 end of the supraorbital canal. Beyond that point the canal continues 

 backward through the squamosal and then through the lateral extra- 

 scapular of Van Wijhe's nomenclature, near the middle of which latter 

 bone it gives off the supratemporal commissure. This lateral extra- 

 scapular bone was found, in both of my two specimens, in two pieces, 

 which two pieces would seem to be the bones B and I of Huxley's 

 descriptions, Huxley apparently considering his bone J as a supra- 

 scapular. Having traversed the lateral extrascapular the canal is said 

 by Van Wijhe to enter and traverse a suprascapular, and beyond that 

 bone to become the lateral canal of the body. On both sides of both 

 my specimens, however, the canal here first traversed a small dermal 

 bone that lies between the extrascapular and the so-caUed supra- 

 scapular. This little bone is quite probably the true suprascapular, 

 the bone designated by that name by Van Wijhe being evidently a 

 supraclavicular, as which it was considered by Gegenbaur [40\ 



The one sense organ of the ethmoidal commissure, on each side, 

 and those in that part of the main infraorbital canal that lies anterior 



Internationale Monatsschrift für Anat. u. Phys. XXI. 31 



