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LABIAL CARTILAGES OF RAIA CLAVATA. 
On a still later page of his work (l.c., p. 222) Gegenbaur 
says that the first (anterior) labial of selachians corresponds 
to the premaxillary bone of teleosts and the second (posterior) 
labial to the maxillary bone of those fishes, and as he includes 
both the Selachii and the Batoidei in the term selachians 
(Selachier), and as he makes no qualification whatever of the 
statement, it evidently implies that the so-called anterior and 
posterior labials of both these sub-orders of the Plagiostomi 
are homologous, which is again in direct contradiction to his 
positive statement made on p. 218. 
T. J. Parker (1884) gives a figure of these labials in Raia 
nasuta which somewhat resembles Gegenbaur’ s figure of 
them in Raia vomer, but the so-called first labial of Parker’s 
descriptions, which is Gegenbaur’s anterior labial, is so long 
that it crosses the opening of the mouth and overlaps ex- 
ternally the mandible. This labial is said to support the 
•corresponding flap of the fronto-nasal process, while the 
second labial, Gegenbaur’s posterior one, is said to lie in a 
fold of skin external to the naso-buccal groove. But as there 
is no fold of skin external to the naso-buccal groove excepting 
only the flap of the fronto-nasal process, this labial is thus 
here said to also lie in that flap. 
W. K. Parker (1878) also gives figures and descriptions of 
these labials in Raia maculat a and Raia clavata, but they 
differ so radically from Gegenbaur’s and T. J. Parker’s figures 
and descriptions that there is no possibility of comparison. 
These several descriptions of the labials of the Batoidei are 
accordingly not clear, and I have, in connection with my 
-present work on the cranial anatomy of Chlamydoselachus, 
-examined these cartilages in such specimens of these fishes as 
I happened to have at my disposal. These specimens con- 
sisted of a single head of Raia clavata, two small speci- 
mens of Raia, r a di ata, two small specimens of Myliobatis, 
and two partly dissected specimens of Torpedo ocellata. 
The head of Raia clavata was a fresh one, while all the 
other specimens had been long preserved in alcohol, and were 
-not in good condition for this particular dissection. 
VOL. 62, PART 1 . NEW SERIES. 
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