168 
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. 
oticus 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 R. 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 7 was found to be want- 
ing. The full complement of sense organs, however, was 
present. 
Right Supraorbital Canal (sw. 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 
commiissure (s. 0. ¢.), 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 
