No. 3.] CHEEK AND SNOUT OF AMIA CALVA. 439 
the mouth is closed, lie entirely internal to the lachrymal and 
first suborbital. In Polypterus the so-called maxillary occupies 
a position corresponding exactly to that of the maxillary, supra- 
maxillary, and suborbital bones together of Amia when the 
mouth is closed, and it is traversed, as the premaxillary in the 
same fish is, by the infraorbital lateral canal. That this canal 
could traverse a bone homologous with the maxillary of Amia 
is even more improbable than in the case of the premaxillary. 
The so-called maxillary of Polypterus must, accordingly, either 
be formed by the fusion of the maxillary bones of Amia with 
certain of the infraorbital bones of the same fish, or the maxil- 
lary bones must either have disappeared in Polypterus, or not 
yet have developed as separate bones, and the infraorbital bones 
must have independently acquired teeth, as the antorbital canal 
bones of Lepidosteus seem to have done. The former supposi- 
tion seems much the more probable, and I assume it to be true. 
As the so-called anterior suborbital bone of Traquair’s descrip- 
tions of Polypterus occupies exactly the position of the lachrymal 
of Amia, and is traversed by the infraorbital lateral canal after 
that canal has left the so-called maxillary, and before it enters 
the premaxillary (No. 44, p. 181), the fusion of the canal bones 
with the teeth-bearing ones must begin with a homologue of 
one of the suborbital bones of Amia. 
Regarding the postfrontal I have nothing to add to what I 
have already said about it in an earlier work (No. 1, p. 478). 
So far as my experience goes, it never in any fish fuses with the 
underlying postorbital ossification. On the contrary, in Scomber, 
where the muscles of the cheek acquire an origin in part from 
the lateral edge of the dorsal surface of the skull, as they do in 
the Characinidae and Cyprinidae (No. 36, p.61; No. 37, p. 501), 
the postfrontal, definitely identified by the canal that traverses 
it, is found on the outer surface of the muscles and not beneath 
them. 
No separate description of the maxillary and supramaxillary 
_ is necessary. 
The preoperculum (POP) is traversed its full length by a 
lateral canal and is developed in connection with, or in relation 
to, the sense organs of that canal. According to Sagemehl 
