> SO 
STRUCTURE AND AFFINITIES OF THE PLATYSOMIDA. 363 
It is unfortunate that the dentition of Wardichthys is as yet unknown, but 
its affinity to Mesolepis seems pretty clear from the osteology of the head, a 
resemblance to Benedenius being also seen in the small size of the dorsal fin 
and the backward position of its commencement. But we have now got the 
deep short body of Chetrodus and Platysomus, as well as the narrow flank scales 
of these genera, the scale ornament being, however, very different from that of 
Platysomus, and more resembling what is found in Cheirodus and Mesolepis. 
Genus VI. Cheirodus, M‘Coy, 1848. 
(?) Platysomus, Binney, 1840. 
Cheirodus, M‘Coy, 1848 (not Pander, 1858) ; Traquair, 1878. 
Amphicentrum, Young, 1866; Hancock and Atthey, 1871; Traquair, 
1875, 
History.—In 1866 Professor YounG* instituted the genus Amphicentrum for 
a remarkable Platysomid fish from the North Staffordshire coal-field, which he 
also distinguished specifically as A. granulosum. A second species, A. striatum, 
from the Coal Measures of Northumberland, was in 1871 added by Messrs 
Hancock and Atruey.t 
Professor Youne’s original description of A. granulosum includes a minute 
account of the osteology of the head, illustrated by a restored outline showing 
the cranial and facial bones. But in 1875 I published a description of the 
cranial structure of the same genus, differing in many particulars of great 
importance from that given by him, especially as regards the determina- 
tion of those dentigerous bones, which so frequently occur in a detached 
condition. Since that time the examination of a considerable number of 
additional specimens from both the North Staffordshire and Lancashire coal- 
fields has amply confirmed these statements, in which I differed from Professor 
Youne, and has also brought to light a few additional particulars, though 
there are still some points regarding which some further information is 
desirable. 
But although to Professor Youne is undoubtedly due the credit of having 
first described and figured an entire specimen of this strange and interesting 
genus, its remains were nevertheless previously not entirely unknown or 
unpublished. As early as 1841+ Mr E. W. Binney figured some scales from 
the Manchester coal-fields as belonging to Platysomus, but which, judging 
* Op. cit., p. 306. 
+ Nat. Hist. Trans., Northumb. and Durham, vol. iv. 1871, p. 414; also in Ann. and Mag. Nat 
Hist., ser. 4, vol. ix. 1872. 
+ Trans. Manchester Geol, Soc, vol. i. 1841, plate v. figs. 14 and 15. 
VOL. XXIX, PART I. 5A 
