MAXILLARY AND VOMER BONES OF POLYPTERUS 369 
long valley between the palatine splints and the maxillary chain 
of canal bones. In embryos this long valley is a large and low 
rounded ridge of the tissues of the roof of the mouth, with a 
slight furrow at either edge, and this ridge probably represents 
the primary upper lip. On the palatine splint there are two 
rows of teeth, the teeth of the inner row being slightly larger 
than those of the outer row. 
In my embryos the outer row of teeth related to the canal . 
bones are somewhat larger than those of the inner row. In the 
adult, on the contrary, the teeth of the inner row are much the 
larger. The smaller teeth of the outer row are, in the adult, 
directly continuous with the premaxillary teeth, the large teeth 
of the inner row ending posterior to the premaxillary teeth, in 
practically the positional relation to them that the dermopala- 
tine teeth of Amia have to the premaxillary ones. External to 
the main row of premaxillary teeth there may be a second, but 
shorter row of teeth. These premaxillary teeth are all large 
ones, similar to those of the inner row of the canal bones. 
There is a well-developed dorsolateral diverticulum of the 
buccal cavity, but it is not prolonged anteriorly as a recognizable 
preangular crease. ‘There is, as in Amia, a tall coronoid process 
to Meckel’s cartilage, and from this process a ligament arises 
and has its insertion on the holostean maxillary. There is no 
maxillary breathing-valve. Itis therefore quite certain that both 
of the rows of teeth related to the canal bones of this fish are 
secondary ones, and those of the outer row quite certainly corre- 
spond to the maxillary teeth of Amia. The teeth of the inner 
row are perhaps similar to those of Polypterus, but it seems 
much more probable that they lie external to the primary lip, 
along a ridge that corresponds to that ridge on the internal 
surface of the labial fold of Amia that encloses the ligament that 
I consider to represent the posterior upper labial cartilage. 
