LIPS AND NASAL APERTURES IN FISHES 183 
also called by me the supramaxillary furrow and was said to be 
the homologue of the similarly named furrow in Amia, but I 
now recognize that there are, in Amia, two partly confluent 
furrows here, one being the labial furrow and the other the 
supramaxillary furrow of the present descriptions. From the 
external opening of this furrow the postlabial portion of the 
labial furrow runs forward in the lower jaw to the hind end of a 
supramandibular fold, and is there continuous with the supra- 
mandibular furrow. When the mouth is closed the functional, 
or tertiary upper lip extends posteriorly across the actual angle 
of the gape and ends at the hind end of the supramaxillary 
furrow, where that furrow and the postlabial furrow are fused 
in their superficial portions, this point forming a tertiary angle 
of the gape and lying posterior to the actual, or secondary 
angle. When the mouth is open, the line of the tertiary upper 
lip is seen to be interrupted for a short distance immediately 
posterior to the secondary angle of the gape. The lateral end 
of the so-called postnasal cartilage of Fiirbringer’s descriptions 
passes between the labial cavity (supramaxillary furrow) and 
the cavity of the mouth, and ends in the mesial edge of the 
short labial fold. This cartilage is thus quite unquestionably 
an upper labial which has been pulled postero-mesially out of ~ 
the labial fold, but there is nothing in this fish definitely to show 
whether it is an anterior or a posterior upper labial. It, how- 
ever, evidently corresponds to the cartilage ‘f? of Chimaera, 
above referred to, and as that cartilage is certainly not a pos- 
terior labial, both it and the cartilage of ceratodus must be 
anterior upper labials. 
SUMMARY AND COMPARISONS 
It is thus seen that there are three distinctly different types 
of lips in the gnathostome fishes, a primary lip, a secondary lip, 
and a tertiary lip, and a band of the external surface of the head 
is added to the functional cavity of the mouth between the 
primary and secondary lips and a second such band between 
the secondary and tertiary lips. The primary lips, as functional 
