Nos. IAND2.] ANATOMY OF SCOMBER SCOMBER. 187 



organ of the line and organ 14 infraorbital is system 14 of the 

 latter line, that system thus being a double system. 



The two sense organs of the line are innervated by branches 

 of the first, large branch of the nervus linese lateralis. 



Organ 14 infraorbital of Scomber is thus the homologue of 

 organ 18 infraorbital of Arnia. It must also be the homologue 

 of organ 4 of the lateral canal of Cole's description of Gadus, if 

 organ 3 of that fish is the homologue of the glossopharyngeal or- 

 gan of Amia, as I have been led to suggest (No. 8, p. 369). 



In Menidia there is, according to Herrick (No. 36), but one 

 sense organ in the supratemporal commissure. 



5. Li)ies of Surface Pit Orgaiis 



But three lines of surface pit organs could be found on the head 

 of Scomber. They correspond, in general position, to the an- 

 terior, middle and posterior head lines of Amia, and are un- 

 doubtedly the homologues of those lines. Their innervation could 

 not be determined. There were usually from five to eight organs 

 in each line. 



The anterior line begins antero-mesial to the terminal pore of 

 the supraorbital canal, approximately dorsal to the posterior or- 

 gan of the canal, and runs backward and mesially to a point 

 slightly lateral to, or lateral and anterior to, the terminal pore 

 of the supratemporal commissure. 



The middle line begins antero-mesial to the point where the 

 preoperculo-mandibular canal joins the main infraorbital canal, 

 and runs mesially and forward for a short distance. 



The posterior line forms, with its fellow of the opposite side 

 of the head, a transverse line across the top of the head, approx- 

 imately between the terminal pores of the supratemporal com- 

 missures. 



No surface indications of any other head lines were found, but 

 there was always a small branch sent backward and downward 

 from the mandibularis externus facialis toward the lower edge 

 of the preoperculum, which may perhaps be destined to supply 

 such a line. 



