350 EDWARD PHELPS ALLIS, JR. 
these two lips was primarily a part of the external surface of the 
head. The teeth on the maxillary and premaxillary bones were 
said to have been developed in relation to the upper one of these 
two secondary lips, and hence to lie external to the primary lip. 
The upper labial cartilages of the Selachii were said to occupy 
a similar position in relation to the secondary lip of those fishes, 
and, whenever a labial fold had been differentiated, to both lie 
in that fold. 
The maxillary and premaxillary bones of fishes, like the 
tooth-bearing bones of all vertebrates, are generally considered 
to have been primarily formed by the fusion of the bases of the 
teeth they bear. Gaupp (05), however, says that while these 
tooth-bearing bones of fishes were undoubtedly thus primarily 
developed, they frequently later become so completely emanci- 
pated from the teeth to which they owe their origin that they 
develop wholly independently of them, never, in certain cases, 
having, ontogenetically, any relation to teeth of any kind, while 
in other cases the teeth and bone may develop independently of 
each other, and the teeth later become implanted on the bone. 
Gaupp then further says that the maxillary-and premaxillary 
bones of vertebrates in general consist of two components, a 
tooth-bearing one derived from fusion of the basal plates of the 
teeth they bear, and a non-toothbearing, or facial portion, of 
independent integumental origin. 
The tooth-bearing bones of the buccal cavity are said by 
Gaupp to probably all have been primarily developed in topo- 
graphical relations to underlying parts of the preexisting car- 
tilaginous skeleton, for there would be no sense in their being 
developed where there was no firm support beneath them. _ The 
underlying structures in relation to which the maxillary and 
premaxillary were developed are said to have probably been, 
primarily, cartilages belonging to the category of the labial 
cartilages, but that, later, secondary relations to the ethmoidal 
cartilage were acquired. Gegenbaur (’98) apparently held a 
similar view, and he considered the underlying cartilages in 
relation to which the maxillary and premaxillary were re- 
spectively developed to be the anterior and posterior upper 
