No. 3.] CHEEK AND SNOUT OF AMIA CALVA. 459 
because of that absorption of its underlying support; the 
dermo-palatines separated from the ectopterygoids and brought 
together in the middle line of the head ; and the auto-palatine 
separated from the dermo-palatine, excepting along the lateral 
edge of that bone, and immovably, instead of movably, articu- 
lated with the preorbitai ossification. 
The posterior surface of the preorbital ossification would then 
form part of the inner wall of the orbit, as its supposed homo- 
logue, the lateral mass of the ethmoid, does in man. Between 
it and the frontal would be found the openings of the internal 
orbital canals, which canals in man transmit the nasal nerve 
and nasal vessels, and in fishes, nasal vessels, and, where it is 
found, the ramus ophthalmicus profundus. 
The auto-palatine would present a free, orbital surface 
between the preorbital ossification and the pterygoid bone, 
with both of which it would be articulated; and it would lie 
immediately internal to and adjacent to the maxillary. 
The lachrymal, if slightly detached from the suborbital bones, 
—or, better still, a dermal prefrontal, if it existed, as Bridge 
says it does, — would lie, as the lachrymal does in man, between 
the preorbital ossification posteriorly, the frontal dorsally, and 
the antorbital anteriorly, the latter bone being the homologue 
of the nasal process of the superior maxillary bone of man. 
The posterior nasal aperture would lie approximately between 
the antorbital bone and the lachrymal or prefrontal, as the case 
may be; and the tube leading from the aperture to the nasal 
sac, or that tube plus a part of the canal that, in embryos, 
connects the tube with the infraorbital lateral canal, would 
correspond closely in its relations to the adjoining bones 
to the lachrymal groove of man. If, then, the naso-lachrymal 
canal of higher vertebrates is developed, as Wiedersheim sug- 
gests (No. 47, p. 313), from some part of the lateral-line canals 
of fishes, the posterior nasal canal of Amia, or its embryonic 
connection with the anterior end of the suborbital lateral canal, 
must be that part. In support of this, it is important to note, 
that in all those animals in which the naso-lachrymal canal is 
found there is but one external nasal aperture on each side of 
the head ; and that the naso-lachrymal canal opens into the nasal 
