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has are arranged more definitely with regard to the pores, 

 i.e., there is always one sense organ between two adjacent 

 pores, except between pores 2 and 3, where a sense organ 

 was absent. The part of the canal innervated by the R. 

 oticiis vii. also differs from that of the ocular side in that 

 it has 3 pores, between the first two of which no sense 

 organ was found, and only the first two sense organs 

 were innervated by the E,. oticus vii. The sense organ 

 corresponding to the third or last otic was on this side 

 innervated from the R. supratemporalis x., and hence 

 belonged to the lateral canal, as in the Cod. 



Hyomandibular canal (hy. c). — This canal anasto- 

 moses behind on the pterotic with the infraorbital on the 

 ocular side, and the lateral on the eyeless, side, as above 

 described. It passes forwards for a little and then turns 

 sharply downwards on to the preoperculum. It courses 

 downwards parallel with the anterior edge of the pre- 

 operculum, turns abruptly forwards with the same, and 

 finally passes over the articular on to the dentary, on 

 which it ends far in front by a pore. The positions of the 

 sense organs and pores are shown in the chart. The 

 canals of the two sides agree in all essential respects, 

 except that in the sections, pore T was found to be want- 

 ing. The full complement of sense organs, however, was 

 present. 



Right Supraorbital Canal (sup. c). — This is the only 

 complete supraorbital in the Plaice, the left being repre- 

 sented only by vestiges. It anastomoses with the right 

 infraorbital between the first and second tuberosities on 

 the frontal, and passes forwards for a short distance, and 

 then gives off almost at right-angles the supraorbital 

 commissure [s. o. c), to join the supraorbital canal of the 

 other side. It then passes forwards in the substance of 

 the right frontal, leaves this in front and passes on to the 



