LIPS AND NASAL APERTURES IN FISHES ges) 
face of the process a and the overlapping naso-labial fold, and 
would remain an incurrent aperture until such time as the 
originally excurrent aperture had acquired its definitive position 
and so become better situated to receive the inflowing current 
of water; provided, of course, that this aperture of Chimaera is 
actually incurrent and not still excurrent. The furrow related 
to the nasal fold would probably become the supramaxillary 
furrow, and if the bottom of this furrow were directed aborally, 
_ it would give rise to a supramaxillary fold which would partly 
overlap the labial fold, as it actually does in Chimaera. The 
space in chiloscyllium, between the nasal and labial folds would 
mark the place of, or actually represent, the vertical furrow 
on the external surface of the nasal-labial fold of Chimaera. 
How these changes could affect the buccalis latero-sensory 
canal to such an extent as to deflect it from its normal course 
and turn it aboral to the nasal apertures is not apparent, but 
the cause, whatever it may have been, must have also been 
operative in the Dipneusti, for this sensory line there also passes 
aboral to both the nasal apertures. In the Amphibia this 
sensory line always lies aboral to the posterior (internal) nasal 
aperture and apparently usually aboral to the anterior (ex- 
ternal) aperture also, but the descriptions that I find are not 
definite as to this. 
TELEOSTOMI 
In the Teleostomi the nasal pit is said (His, ’92b) to lie, in 
embryos, on the ventral surface of the snout, as it does in the 
Plagiostomi and Holocephali. Peter (’06) says that the pit 
develops late in these fishes, and that when the two nasal aper- 
tures later shift from the ventral to the dorsal surface of the 
snout they always retain their relative positions in relation to 
the upper edge of the mouth, the anterior aperture of embryos 
thus being the posterior aperture of the adult. There is ap- 
parently a slight rotation of the line of these apertures in 
the opposite direction to that in which they rotate in the 
Plagiostomi, and there may be some rotation of the line of the 
median raphe of the Schneiderian membrane, for Burne (’09) 
