LIPS AND NASAL APERTURES IN FISHES il 
gle, extending from in front mesially and slightly orally, the antero- 
lateral aperture leading orally into the postero-lateral end of 
the fenestra nasalis and the postero-mesial aperture leading 
aborally into its antero-mesial end. The long axis of the fenestra 
nasalis and the median raphe have accordingly here both*swung 
partly round a circle, dragging the external apertures after them, 
as in Acanthias. 
The postero-mesial two-fifths of the edge of the fenestra nasalis 
of this fish is of membrane, the remaining three-fifths of cartilage. 
The ala nasalis (Nasenfliigelknorpel) encircles about four fifths 
of the fenestra and fits against the inner edge of its cartilaginous 
portion, the mesial end of its oral limb projecting mesially beyond 
the cartilaginous portion of the fenestra and there lying largely 
external to the fenestra and hence outside the nasal capsule. 
That part of the ala nasalis which lies against the inner edge of 
the cartilaginous portion of the fenestra is there strongly at- 
tached to the inner surface of the nasal capsule by connective 
tissues, but it is nowhere fused with the capsule. It lies against 
the internal surface of the inner lining membrane of the capsule ’ 
and is strongly attached to it, and this membrane, in my pre- 
served specimens, lies closely against the membrane forming the 
membranous postero-mesial portion of the capsule. The two 
membranes can, however, be easily separated from each other, 
and it is to the inner lining membrane and not to the outer that 
the ala nasalis is here attached. It is furthermore this inner lining 
membrane of the capsule which alone connects the free mesial 
ends of the oral and aboral limbs of the ala nasalis, no membrane 
representing an unchondrified portion of the nasal capsule, such 
as Gegenbaur (’72) describes in this and others of the Plagiostomi, 
existing here. There is however a stout thick membrane, 
which doubtless includes the perichondrial membrane, which lies 
closely upon the external surfaces of the nasal capsule and the 
ala nasalis, thus binding them together, but this membrane is 
not an unchondrified portion of either of these cartilages and can 
be easily stripped from them. 
The lateral portion of the ala nasalis, together with the pro- 
cesses a, a’ and 6 of Gegenbaur’s descriptions, encircles the in- 
