364 RAMSAY H. TRAQUAIR ON THE 
from the figures, have undoubtedly a much greater resemblance to those of 
Professor Youne’s fish. And during a recent visit to the Woodwardian 
Museum at Cambridge I was surprised to find that the original specimen 
described by M‘Coy in 1848* as Cheirodus pes-rane, and considered by him 
to be the tooth of a Cestraciont allied to Ceratodus, then still ranged among 
the sharks, was in reality nothing more than a mandibular dental plate of | 
the same Platysomid genus. I have, therefore, in a recently published paper,t 
felt compelled by the inexorable law of priority to propose the abolition of 
““ Amphicentrum,” however much we may regret the necessity for supersed- 
ing a name by which the animal in its entirety is so widely known, by one 
which was originally bestowed upon a mere fragment whose nature its describer 
did not understand. 
Since the discovery of the true position of Ceratodus, Cheirodus, M‘Coy, has 
been associated with the Dipnoi, both on account of M‘Coy’s original opinion 
of its affinities, and because PANDER{ not only referred to the same genus the 
teeth from the Devonian of Russia, which he named Cheirodus Jerofejewi, but 
also merged in it the Conchodus of M‘Coy, which he considered to have been 
founded on the palatal tooth-plate of a fish generally identical with that whose 
mandibular one constituted Cheirodus pes-rane. But it is now clear that 
Cheirodus, Pander, is not = Chetrodus, M‘Coy, though it is indeed possible that 
the former may be identical with Conchodus, the Dipnoous nature of which is 
undoubted. 
Species.—One unfortunate circumstance connected with the establishment 
of species upon mere fragments, like M‘Coy’s Chetrodus pes-rane, consists in 
the difficulty which we so often experience in satisfactorily deciding as to the 
identity or non-identity with them of more perfect specimens from other 
horizons or localities. The difficulty is seriously felt in the case of Cheirodus, 
and although I have, in my paper last referred to, felt inclined “ pes-rane,” 
M‘Coy, and “granulosus,” Young, as best kept separate, I must nevertheless 
own that this view of the case is also open to serious doubt. In any case the 
retention of Professor Youne’s specific name seems justifiable, on the ground 
that M‘Coy’s specimen is hardly sufficient to characterise the species, although, 
on the other hand, the genus to which it belongs is unmistakable. The only 
other species known is C. striatus of Hancock and ATTHEY. 
Geological Position.—This is entirely a Carboniferous genus. C. pes-rane, 
M‘Coy,is from the Carboniferous Limestone of Derbyshire, and Mr W. J. BARKAS 
has recorded the occurrence of C. granulosus in the same formation at Rich- 
* Ann, and Mag. Nat. Hist. ser. 2, vol. ii. 1848, pp. 130-131. British Paleozoic Fossils, p. 616, 
plate 3 g, fig. 9. 
+ Ann. and Mag. Nat. Hist., July 1878, pp. 15-17. 
} Die Ctenodipterinen des Devonischen Systems, St Petersburg, 1828, pp. 33-37, plate vi. 
figs, 15-22. 
