178 EDWARD PHELPS ALLIS, JR. 
developed in relation to the supramaxillary fold, but marked 
tooth-like spines may be developed in relation to it, as on the 
lacrimal bone of Scorpaena (Allis, ’09). 
In the Chondrostei the conditions are markedly different from 
those in the other Teleostomi, and I am unable to give a definite 
opinion regarding them. In my earlier work (Allis, ’00), I came 
to the conclusion that the labial fold, there called the maxillary 
fold, was represented in a fold of dermal tissues shown by 
Parker (’82) extending across the snout of larvae of Acipenser, 
immediately anterior to the barbels of the fish. This fold is not 
shown either in my figures (Allis, ’04) of the adult Acipenser or 
in those of Scaphirhynchus, but in both of these fishes the 
anterior portion of the buccalis latero-sensory canal has ap- 
proximately the position of the fold in larvae of Acipenser. It 
is therefore probable that ‘this fold in the larvae of Acipenser is 
the supramaxillary fold of the present descriptions, and hence 
not a maxillary fold as I formerly concluded; and it passes, as 
the fold does in Gadus, between the upper edge of the mouth 
and the nasal apertures. The primary lips of both Acipenser 
and Scaphirhynchus are certainly represented in some important 
part of the lips of the suctorial mouth of these fishes. Whether 
or not secondary lips are also represented in some part of the 
lips I can not determine. If present there, they are quite cer- 
tainly rudimentary and found only at the angle of the gape, and 
it may be that they are wholly wanting. In Polyodon, also, 
the secondary lips, if present, are found only at the angle of the 
gape, this rudimentary condition of the secondary upper lip 
doubtless accounting for the absence of a premaxillary bone in 
all these fishes, and for the peculiar position and character of 
the maxillary splint in Polyodon. The conditions in these fishes 
however need further investigation. 
DIPNEUSTI 
In embryos of Ceratodus the nasal groove, as shown by 
Semon (’93) and Greil (’13), is, when first formed, directed 
postero-mesially, as it is in embryos of the Selachii, but it later 
