MAXILLARY AND VOMER BONES OF POLYPTERUS 367 
contact with the parasphenoid, and their hind ends lie, even in 
the adult, ventral to the anterior ends of the ectopterygoids. 
The position of these bones of Polypterus thus, in itself, indi- 
cates that they are quite probably not the homologues of the 
unpaired vomer of the Teleostei, which bone lies in part 
directly upon the base of the chondrocranium, and in part 
directly upon the anterior end of the parasphenoid, and con- 
clusive proof of the non-homology of these bones is given by 
the conditions in Macrodon. In the latter fish Sagemehl (’84) 
describes an accessory palatine which is said to be but loosely 
bound to the other bones of the palatine arch, and to be un- 
known in other fishes. I find these bones of Macrodon having 
exactly the relations to the other bones of the palatine arch 
that the so-called vomers of Polypterus have, and I have twice 
suggested (’00, p. 278, and ’09, p. 26) that they might be the 
homologues of the latter bones. I, however, then considered 
these bones of both these fishes to have been developed in the 
maxillary breathing-valve of the fish, which, as my present work 
shows, is incorrect in so far as Polypterus is concerned, and ref- 
erence to Miiller and Troschel’s (’45) figure of the widely opened 
mouth of Macrodon shows that it is incorrect for that fish also, 
for what is apparently a well-developed maxillary breathing-valve 
is there shown, and the accessory palatine lies posterior to it. 
It is thus certain that the so-called vomers of Polypterus do 
not contain the homologue of the basal plate of the unpaired 
vomer of the Teleostei. The teeth implanted upon that basal 
plate may, however, be the homologues of those of Polypterus, 
for with the disappearance of the suprapalatine recess and the 
disintegration of the mesial portions of the palatine processes of 
the palatoquadrates, these teeth of Polypterus would lie directly 
superficial to a vomer such as is found in Macrodon, and if they 
persisted they would necessarily become implanted upon it. And 
in accord with this view, the vomer of Macrodon is non- 
dentigerous (Sagemehl, ’84). 
The vomer of the Teleostei is thus quite probably formed of 
two primarily independent components, one dermal and the 
other dental, but this may possibly not apply to the paired 
