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portion of the bone near its hind edge. This section of canal contains 
three sense organs, which are the sixth, seventh, and eighth of.the 
entire line. Between the sixth and seventh organs there is a tube 
directed backward and downward and opening by a single pore; and 
between the seventh and eighth organs there is a tube directed back- 
ward, or backward and upward, and also opening by a single pore, 
the eighth one of the line. All of these eight pores le in the tough 
dermis that covers the several related bones, those in the mandible 
lying directly mesial to the deep furrow that extends upward into the 
lower lip of the fish. Near the dorsal edge of the preoperculum the 
canal ends in a single terminal tube and pore. .This pore, which is 
the ninth one of the line, lies at the postero-ventral corner of the 
posterior spiracular ossicle, in the narrow band of tough dermis that 
lines the ventral edges of the spiracular bones. The canal between 
tubes eight and nine turns somewhat forward so that these two pores, 
and pore ten infraorbital, lie in a nearly straight line directed down- 
ward and slightly backward. 
COLLINGE states positively that the preopercular canal joins, at 
its dorsal end, the main infraorbital canal, and he shows in his figures 
a small canal traversing the prespiracular, spiracular, and postspira- 
cular ossicles, this canal being said to establish the connection. Diligent 
search has failed to show such a canal in any of my specimens, and if 
it existed in any of the specimens CoLLINGE examined it certainly could 
not have been a lateral sensory one. POLLARD, in the figure he gives 
of the canals of the fish, shows the main preopercular canal itself ex- 
tending dorsally through the posterior spiracular ossicle to join the 
main infraorbital canal. He, however, states, in another work (No. 12), 
published at the same time, and as CoLLINGE has pointed out, that 
“the opercular canal does not join the main canal”. This, according 
to him erroneus observation, COLLINGE also attributes to me, over- 
looking the fact that my statement was a simple reference to Tra- 
QUAIR’S work. i 
This completes the description of the canals of Polypterus, and 
the enumeration of the sense organs that they lodge. In addition to 
these enclosed sense organs there are, on each side of the head of 
Polypterus, six short Lines of Surface Sense Organs, each 
line occupying a slight depression on the outer surface of the related 
bone. Each line apparently contains several sense organs, and there 
are, on each side, two on the dorsal surface of the head, three on the 
cheek, and one on the ventral surface of the head. They unquestion- 
