THE SENSORY CANAL SYSTEM OF FISHES. 509 
with the supra-orbital branch,—thus bringing about a con- 
dition not at present known to occur in any other investigated 
fish. 
Following the coalescence of these two branches on the ven- 
tral surface of the rostrum, the course now lies forwards and 
inwards, the canal being conducted by a series of canal bones, 
to which reference will be made later. It continues forwards, 
diverging laterally in the anterior portion, and meets with its 
fellow of the opposite side. 
Traversing the lateral and posterior portion of the parietals 
are two small branches passing from the main canal towards 
the median line, but which, however, do not form a commis- 
sure. The hyomandibular branch, as previously pointed out, 
passes off from the posterior lateral border of the dermo- 
sphenotic. It is continued as a dermal canal to the angle of 
the mouth, where it divides into two finer branches, the dorsal 
one passing along part of the maxilla, and the ventral one along 
the mandible. A series of small branches pass off from the 
hyomandibular portion and are distributed over the opercular- 
flap, and terminate in cluster and primitive pores (Pl. 39, fig. 
3, ¢c. p. and p. p.). 
It will be seen from the preceding account that the system, 
in so far as the canals and branches are concerned, is one of a 
very simple character. 
We will now examine the various branches, pores, &c., in 
detail. 
1. Tue Lateran Canat.—Commencing about 180 mm. 
from the tip of the dorsal caudal fin as a fine dermal 
canal giving off numerous branches, the lateral canal passes 
forwards and downwards, and then dorsally again after this 
slight ventral flexure. It continues along the dorso-lateral 
border of the body, becoming dorsal previous to entering upon 
the head. During its course from the caudal to the cranial 
region there is a gradual, but distinctly appreciable, enlarge- 
ment in its diameter. 
There are from thirty-two to thirty-five branches given off 
during the whole length of the canal, of which twelve are 
