The Lateral Sensory System in the Muraenidae. 161 



posterior portion of the squamosals of Amia, Polypterus, and certain 

 other teleosts. The possibility or even probability of such an homo- 

 logy, I have had already occasion to refer to (No. 4), and it is here 

 again referred to because of the exceptional conditions found in Conger. 

 In this fish an ossicle without related organ occupies the region bet- 

 ween the hind end of the otic section of the squamosal canal and the 

 supratemporal commissure; this commissure lies directly dorso-mesial 

 to the dorsal end of the preopercular canal; and there is no pre- 

 commissural organ innervated by a postauditory nerve. The commissure 

 thus corresponds, in certain respects, to the middle head line of pit 

 organs of Amia and the other fishes above referred to, while in others 

 it corresponds to the supratemporal commissure of those fishes. That 

 it is the commissure and not the middle head line seems to me de- 

 finitely proven by the position of the corresponding commissure in 

 Muraena helena; and there is, moreover, a transverse line of surface 

 sense organs having quite definitely the position of a middle head line, 

 as will be later described. 



Are then the post-squamosal ossicles of Conger and Gadus homo- 

 logous, and do they represent in those fishes the posterior portion of 

 the squamosals of Amia, Polypterus, and certain teleosts? And if so 

 why is there no related organ in Conger? These are questions to 

 which my work gives no definite solution, though a very probable 

 solution will be later referred to. My work does however definitely 

 show that the dermal component of the squamosal element of the skull 

 is not of equal value in all fishes. 



Surface sense organs. 



Several well-defined lines of surface sense organs are regularly 

 found on the head of each of the several Muraenidae examined, and 

 are shown in the drawings. Other, scattered, and less important 

 organs are also found, but are not shown in the drawings. These surface 

 organs were more particularly studied in Conger. In this fish certain 

 of the organs that are arranged in lines are larger than the others, 

 and certainly belong to the same category as the pit-organs of Amia 

 and certain other fishes, the remaining ones seeming to represent two 



Internationale Monatsschrift für Anat. u. Phys. XX. 11 



