abe ‘EDWARD PHELPS ALLIS, JR. 
strongly developed. This mandibular labial flap and labial-flap 
furrow both lie external to the mandibular labial cartilage, and, 
because of this, they were called, in my descriptions of other 
Selachii (Allis, 718), the supramandibular fold and furrow, but 
the names above given to them seem more appropriate. Another 
deep furrow lies internal to the mandibular labial cartilage, and 
is the mandibular furrow of my recent work, but sublabial fur- 
row seems a better name for it. This sublabial furrow is con- 
tinuous, posteriorly, with the postlabial furrow, a labial fold with 
both maxillary and mandibular portions thus being formed. 
A deep furrow extends upward between the hind ends of the 
anterior and posterior upper labial cartilages, and extending 
laterally (morphologically posteriorly) from the secondary angle 
of the gape across the labial fold, falls into the postlabial furrow. 
This furrow thus separates the lateral (morphologically posterior) 
portion of the labial fold into two parts, a superficial one which 
encloses the anterior upper labial and a deeper one which en- 
closes the posterior upper and mandibular labials. This furrow 
may be called the submaxillary one, because in the Holostei 
and certain of the Teleostei, it lies beneath the hind end of the 
maxillary bone. In the fishes described in my earlier work 
(Allis, ’18) this furrow was but slightly developed, this being due 
to the fact that the hind end of the anterior upper labial there 
articulated with, or was bound by ligament to, either the 
posterior upper or mandibular labials. 
The primary upper lip of Acanthias is strongly developed, and 
between it and the pterygopalatine teeth there is a deep sulcus, 
which may be called the primary superior alveololabial sulcus. 
A maxillary preangular crease, such as I described in my recent 
work, runs symphysially and aborally from the angle of the 
primary gape, and gradually vanishes on the oral surface of the 
labial fold, this crease lying external to the primary upper lip, 
but internal to the posterior upper labial. If teeth were to be 
developed internal (oral) to this preangular crease, they would 
evidently still be secondary teeth, but they would not be the 
homologues of teeth developed along the edge of the labial fold. 
The crease is continuous, posteriorly, with the anterior end of 
