100 
EDWARD PHELPS ALLIS. 
extends from the middle of the mesial portion to the mesial 
end of the lateral portion. The mesial portion lies quite 
closely upon the palatoquadrate, but is separated from it by 
Tranches of the nervus trigeminus and other tissues. Its 
mesial end projects antero-mesially beyond the palatoquadrate. 
The antero-mesial end of the lateral portion of the labial lies 
against the posterior surface of the nasal capsule, the 
remaining portion lying external to the muscles of the 
region, but separated from them by tough connective tissues, 
the cartilage being bent in conformity with the shape of the 
underlying structures. The postero-lateral portion of this 
lateral portion of the labial lies immediately beneath the 
external dermis and parallel with it, and its posterior end 
lies at a considerable distance from the angle of the gape, 
separated from that angle by the bulging muscles of the 
region. The connective tissues in which it lies are attached 
to it, but it cannot be said that the cartilage runs gradually 
into ligamentous tissues that are continued into the mandible, 
as Gegenbaur says is the case in Raia vomer. 
The narrow neck of cartilage that connects the mesial and 
lateral portions of the labial lies in the hollow between the 
aboral edge of the palatoquadrate and the posterior wall of 
the nasal capsule, and it is always somewhat bent or twisted. 
In my specimens of Raia radiata this twist is so pronounced 
that the primarily posterior (oral) edge of the cartilage is 
presented ventrally, the cartilage thus here lying, as Gegen- 
Tauer has said for Raia vomer, in a vertical position. The 
primarily external surface of the neck was thus, in these 
specimens, presented anteriorly instead of ventrally, and the 
nasal-flap furrow, having crossed the primarily posterior 
(oral) edge of the labial, had, anterior (aboral) to that edge, 
somewhat the appearance of lying on the internal rather 
than the external surface of the labial. 
There were, in my specimen of Raia clavata, no special 
ligamejitous attachments of the mesial (sympliysial) end of 
either the labial cartilage or the nasal-flap cartilage to the 
ventral surface of the rostrum, such as Gegenbaur describes 
