96 
EDWARD PHELPS ALLTS. 
labial; and the lateral (absymphysial) end of the latter cartilage 
is said to be in contact with the palatoquadrate. There is 
accordingly no space either between the adjoining edges of 
the two cartilages, or between their posterior (oral) edges and 
the palatoquadrate, and the nasal groove (Nasenrinne) must 
accordingly lie either wholly lateral (absymphysial) to both 
labials or external to them. 
In Raia vomer the posterior labial is said to be overlapped 
externally, in its middle portion, by the broad lateral (absym- 
physial) portion of the anterior labial, the latter labial thus 
not here having the markedly anterior and aboral relations to 
the other labial that it has in Raia (spe'cies not given). It 
however has the same absymphysial relations to that cartilage. 
The nasal g'roove (Nasenrinne) is apparently shown (l.c., 
PI. 16, fig. 7) lying between the lateral (absymphysial) ends 
of the two labials, but it is said that both labials lie, in part, 
in the nasal flap, and hence necessarily external to the nasal 
groove, as will be later fully explained. The anterior labial 
is referred to, both in the figure and in the text, by the index 
letter L , while in Raia (species not given) that letter refers 
to the posterior labial. 
In Rhinoptera, Gegenbaur says (1. c., p. 219) that there are, 
in addition to a cartilage that corresponds strictly to the so- 
called anterior upper labial of Raia, two small cartilages 
found near the angle of the gape of the mouth which together 
form a rudimentary labial arch similar to the arch formed 
by the posterior upper and the single lower labials of the 
Selachii. The presence of this posterior pair of labials in 
Rhinoptera is said by Gegenbaur to definitely confirm his 
already expressed conclusion that the other labial of Rhino- 
ptera must be the anterior upper one. But it also evidently 
proves, if correct, that the so-called anterior upper labial of 
Rhinoptera, and hence also the corresponding labial of Raia, 
must be the homologue of the similarly named labial of the 
Selachii and not of the posterior one; which is in direct con- 
tradiction to the positive statement made on p. 218 of his 
work and already above referred to. 
