362 EDWARD PHELPS ALLIS, JR. 
there is, in this fish, no maxillary breathing-valve, that valve 
being formed, as already explained, by the anterior portion of 
the primary lip. 
In the lower jaw there are two furrows that correspond, in 
their relations to the lower lip, to the supralabial and maxillary 
labial-flap furrows in the upper lip. One of these furrows 
separates the dermal flap of the lower lip from the remainder of 
that lip, and is the mandibular labial-flap furrow. Like its 
fellow in the upper lip, it begins far forward and extends pos- 
teriorly to the ventra end of the labial cartilage, being deep in 
its middle portion and vanishing at either end. The other 
furrow is a sublabial one, and separates the mandibular portion 
of the labial fold from the external surface of the mandible. It 
begins anteriorly in about the transverse plane o! the anterior 
end of the supralabial furrow, and there lies, like that furrow, 
internal to the free edge of the related labial flap. Posteriorly 
it becomes deeper, and at its hind end passes upward beneath the 
hind end of the labial fold and is confluent with the hind end of 
the supralabial furrow. These two mandibular furrows lie, the 
one directly beneath the lateral edge of the oral surface of the 
lower lip and the other beneath the mesial edge of that surface 
(figs. 8 to 11). The lip here presents, in transverse sections, 
three surfaces, one presented mesially, one dorsolaterally, and 
the other ventrolaterally. The surface that is presented dorso- 
laterally increases in width posteriorly, and at the angle of the 
gape coalesces with the internal surface of that posterior portion 
of the maxillary portion of the entire labial fo'd that encloses the 
labial cartilage. Along the median line, approximately of this 
surface of the lower lip, there is a furrow formed by a fold in the 
lip that is related to its attachment to the top of the ascending 
process of the splenial, this furrow corresponding approximately 
to the mandibular preangular crease of Acanthias. Internal to 
the lip, between it and the dentary teeth, there is a secondary 
inferior alveololabial sulcus, and between the dentary and 
splenial teeth a primary inferior alveololabial sulcus. 
When the upper and lower lips have coalesced at the angle of 
the gape, as above explained, the labial fold projects ventro- 
