154 EDWARD PHELPS ALLIS, JR. 
drical band, slit along the surface presented toward the excurrent 
aperture. The two edges of this slit are apposed and form the 
nasal valve and its valve-seat. Short horn-shaped processes 
arise from the mesial (ventral in Chlamydoselachus) surface of 
this cylinder, one on either side of the valvular slit, and, pro- 
jecting mesially (or ventrally) and curving toward each other, 
partly surround the excurrent aperture. The mesial (or ventral) 
ends of these two latter processes are not connected with each 
other in my specimens of either of these fishes, thus completing 
the alar rg as shown in Gegenbaur’s figure of Heptanchus, and 
the cartilage is nowhere fused with the outer edge of the nasal 
capsule. The cartilage is strongly attached to the outer edge of 
the capsule by ordinary connective tissues, and it is also attached 
to the inner lining membrane of the capsule. In both Hep- 
tanchus and Chlamydoselachus the lateral edge of the nasal flap 
is attached to the external edge of the process aa’, the full length 
of the process a, and, because of this attachment, there is no 
passage connecting the two nasal apertures, between the flap 
and the nasal valve. No part of the ala nasalis actually enters 
the nasal flap, but the process a lies along the internal surface of 
the lateral edge of the flap. 
In Chlamydoselachus the secondary upper lips are, as- slvaade 
stated, short, and they lie oral to the nasal apertures. In Hep- 
tanchus these lips also lie oral to the nasa' apertures, but they 
are much longer than in Chlamydoselachus, and, so far as I can 
tell from my one much dissected specimen, they extend forward 
to the symphysis and there fuse with each other, a continuous 
band of the external surface of the head, concentric with the 
upper edge of the primary cavity of the mouth, thus here being 
added to that cavity. 
In Sceyllium canicula (fig. 5) I find the ala nasalis practically as 
described by Gegenbaur (’72), the process a lying in the lateral 
edge of the nasal flap and the process 6 lying in the lateral edge 
of a groove which forms the seat for the flap. The nasal valve 
is formed by a small fold of mucous tissue which projects mesially 
from the internal surface of the nasal flap and crosses the aboral 
end of the process 6, and there is no cartilaginous process a’ de- 
