MAXILLARY AND VOMER BONES OF POLYPTERUS 365 
coalesced with, or never been completely separated from, the 
tissues of the roof of the mouth. 
The lips and labial folds and furrows of Polypterus are thus 
strictly comparable to those of Acanthias, and the labial fold is, 
as in that fish, a maxillomandibular one. The labial cartilage, 
which lies in that fold, must then be the homologue of one or 
more of the labial cartilages of Acanthias. If the labial flaps of 
Polypterus are the homologues of those of Acanthias, as seems 
so probable, the anterior upper labial must be greatly reduced, 
if not wholly wanting, in Polypterus; and as the labial cartilage 
of Polypterus seems definitely related to the upper lip, the 
mandibular labial must also be greatly reduced, or wholly want- 
ing. The labial cartilage of this fish is thus certainly in large 
part a posterior upper one, remnants only, at the most, of the 
other labials persisting. Pollard’s conclusion (’95, p. 407), that 
this labial is a coronoid one, is then certainly in error, if, as the 
name coronoid would seem to imply, the labial was considered 
by him to be a mandibular structure. 
The premaxillary teeth of my 75-mm. specimen are implanted 
upon a bone that lies in part along the ventral surface of the 
anterior end of the ethmoidal cartilage, and in part encloses the 
ethmoidal section of the infraorbital laterosensory canal, and 
they are apparently, as already explained, secondary teeth and 
the homologues of the corresponding teeth of the Holostei and 
Teleostei. 
The anterior maxillary teeth are implanted upon a plate of 
bone that corresponds to the palatal process of the maxillary 
bone of the adult, and that lies in a layer of fibrous tissue that lies 
slightly internal to the epithelial lining of the buccal cavity. 
This plate lies, in its anterior portion, beneath, but not directly 
against, the cartilage of the nasal capsule, and in its posterior 
portion directly beneath the anterior end of the palatoquadrate 
cartilage. It extends mesially beyond the primary alveolo- 
labial sulcus, to the mesial edge of the vomer, and the anterior 
maxillary teeth arise from its lateral edge and issue, as already 
stated, along the line of the primary lip. The bone is somewhat 
thickened along its lateral edge, where the teeth are implanted 
