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questionably be the homologue of the pedicle, or processus basalis, 
of the amphibian. And as this pedicle in amphibians is generally 
considered to represent the dorsal end of the mandibular arch, the 
process in Chlamydoselachus, if it be its homologue, would necessarily 
also represent the dorsal end of that arch; this adding one more to the 
several suggestions that have already been made regarding the position 
of the dorsal end of this arch in fishes. 
GEGENBAUR, because of the conditions found by him in Hexan- 
chus and Heptanchus, considered the dorsal end of the mandibular 
arch of all of the Plagiostomata to be represented in that part of the 
palato-quadrate that, in Heptanchus, articulates with the postorbital 
process of the neurocranium. Huxuev (1876) considered this ar- 
ticulation in Heptanchus as “‘an altogether secondary connection,” 
and he homologized the part of the palato-quadrate here concerned 
with the otic process of the amphibian, a conclusion that has since 
been very generally accepted and with which my work is wholly in 
accord. Huxrey then says that: ‘The dorsal and posterior edge of 
this (otic) process no less clearly corresponds with the spiracular 
cartilage in Cestracion, otherwise absent in Notidanus’’; the spiracular 
cartilage, when found, thus evidently being considered by Huxuey 
as an integral but detached portion of the otic process. With this 
conclusion PARKER (1876) affirms his fullest accord; but it is to be 
especially noted that the spiracular cartilage of the plagiostomes, so 
far as can be judged from the descriptions given, lies postero-mesial 
to the levator maxillae superioris muscle, and that it can not accor- 
dingly well be a part of the otic process of those fishes. 
This articular process of Heptanchus thus being considered by 
HUXLEY as an otic process, it evidently could not represent the dorsal 
end of the mandibular arch, and Huxtry was accordingly led to look 
for that dorsal end in the orbital process, described by him as “‘an 
inward process” of the palato-quadrate. Of this process he says 
that it “answers to the pedicle of the suspensorium in the Amphibia,” 
that process being said, in an earlier work (1874), to be a part of the 
pterygoid and to “appear’’ to represent the morphologically dorsal 
end of the mandibular arch. Parker (1876), although affirming the 
“happiest conformity” of his views, even in details, with those of 
Professor Huxuny, nevertheless finds (l. ec. p. 204 and 210) the “true 
apex’ of the mandibular arch, in Scyllium, to be represented, not 
in the orbital (palato-basal) process, but in a so-called metapterygoid 
