LIPS AND NASAL APERTURES IN FISHES Bliss 
nasal capsule and supports a fold of mucous tissue which repre- 
sents one-half of the nasal valve. On the opposite side of the nasal 
opening, and beneath the nasal flap, is another mucous fold, which 
forms the other half of the nasal valve, but is not supported by 
cartilage. These two halves of the nasal valve do not, in my 
specimen, meet in the median line of the nasal pit, but they and 
the thicker part of the pad on the internal surface of the lateral 
edge of the nasal flap together form a partition across the pit. 
In contact with the lateral edge of the ala nasalis, but not fused 
with it, a narrow band of cartilage arises, and running inward, 
is at first closely attached to the lining membrane of the capsule, 
but soon separates from that membrane and lies in relation to 
the median raphe of the Schneiderian membrane. ‘This raphe is 
directed mesially and slightly orally, and coincides, in direction, 
with the line of the external nasal apertures. The postero- 
mesial edge of the nasal capsule is membranous, and the naso- 
buccal groove passes over this membranous portion of the 
capsule. 
The naso-buccal groove is large, and extends orally and slightly 
laterally from the postero-mesial nasal aperture to the anterior 
edge of the mouth. In my work on the labial cartilages of this 
fish (Allis, 16) I called this groove the nasal-flap furrow, the naso- 
buccal groove being considered to be a secondary differentiation 
of this furrow and to be represented in a deeper, lateral portion 
of the entire furrow. My present work confirms the opinion 
there expressed that the entire groove is primarily derived from 
the nasal-flap furrow, and that the lateral and deeper portion of 
the groove is a secondary differentiation, but comparison with 
the conditions in Seyllium canicula, as now interpreted, shows 
that it is the mesial portion only of the entire groove which is 
derived from the nasal-flap furrow, the deeper, lateral portion 
of the groove being formed by the crease which, in Seyllium, 
separates the crest of the fold of the secondary upper lip from 
the primary lip, together with the maxillary preangular labial 
crease. . If these two creases of Scyllium were to coalesce and 
then be extended forward until they fell into the naso-buccal 
groove of that fish, the naso-buccal groove of Raia would be 
