LABIAL CARTILAGES OF RAIA CLAVATA. 
103 
somewhat the position of the narrow strip found along the 
ventral edge of the posterior wall of the nasal capsule in 
Raia cl a vat a, and already described. In the other speci- 
men the canal is enclosed in an independent tubule of tissue 
that has a semicartilaginous appearance. In Trygon 
tuberculata Gregenbaur describes (l.c., p. 220) and figures 
what would seem to be a strictly similar tubule, but it is said 
by him to be a rod; and although he says that this so-called 
rod is of fibro-cartilage, he nevertheless considers it to be the 
homologue of the anterior upper labial of his own descriptions 
of Raia and Myliobatis, which latter labial is said to be of 
hyaline cartilage. The lateral portion of this tubular or rod- 
like cartilage of Trygon is shown, in Gfegenbaur’s figure, 
lying definitely internal to the ala nasalis, and it seems as if it 
must accordingly lie, as does the latero-sensory tubule in my 
specimen of Myliobatis, internal also to the nasal-flap furrow. 
If such be the case it cannot be a nasal-flap cartilage, or 
so-called anterior labial, of this fish. It probably contains, 
in both Trygon and Myliobatis, a remnant of the upper 
labial of the present descriptions. If not, then that upper 
labial is entirely wanting in my specimens of Myliobatis, as it 
was in those examined by Gregenbaur. The cartilage described 
by Gregenbaur, in Myliobatis, as the posterior upper labial I 
could not find in my specimens. 
In Torpedo ocellata I find the nasal flap much less long, 
antero-posteriorly, than the flap of Myliobatis, this being due, 
as Gregenbaur has said, to the nasal capsules lying nearer the 
anterior edge of the mouth. The nasal flap is supported by 
a marked prolongation and development of the ala nasalis, 
similar to the prolongation of that cartilage in Myliobatis, 
but there is no indication of a separate nasal-flap cartilage. 
The frenulum is supported by a small median Trager der 
Nasenfliigelknorpel, as in Myliobatis, and the posterior (oral) 
end of this little cartilage is strongly attached by connective 
tissues to the adjoining mesial (symphysial) ends of the 
palatoquadrates of opposite sides. No upper labial cartilage 
was found, and a cord of connective tissue lying internal 
