On the Fossil Fishes of the Carbomferous Limestone Series of Great Britain. 383 
prominence, with which they are connected by a prominent sharp-curved intervening 
ridge ; anterior coronal surface marked with sharp more or less irregular costae, which 
converge intheintermediate crest, producingafaint denticulation, sometimes forming 
quite strong spinous processes.” ‘Theform described by Dr. Newberry under the name 
of Carcharopsis worthent, is regarded as a typival representative of the genus first 
recognized by Prof. Agassiz, and intimately allied to, though probably specifically 
distinct from Pristicladodus dentatus of M‘Coy, whether the latter is identical with 
the original form named by Agassiz Carcharopsis prototypus or not, the authors have 
not been ableto ascertain, but “in assigning to each of those groups appellations which 
we believe to have been originally applied to quite different forms, in part at least, 
by Profs. Agassiz and M‘Coy, we have been guided by such facts as are accessible 
to us, only desiring to render due justice to our own authorities.” 
After consideration of the several descriptions given above, it appears that the 
Carcharopsis of Agassiz was a tooth consisting of a crown formed of a single cusp or 
cone, deeply plicated or folded towards the base, the latter was much contracted in 
size compared with the diameter of the crown. M‘Coy’s genus Pristicladodus is 
also well defined, having a broadly expanded horizontal base resembling Cladodus, 
and in some instances a single lateral cone on each side the central one : the type 
species, C. dentatus, however, was not possessed of lateral cones. The specimens 
described by Newberry as Carcharopsis wortheni bear so close a resemblance to 
Pristicladodus dentatus, M‘Coy, that there can be no doubt that it should be trans- 
ferred to that genus. The genera Carcharopsis, Ag., and Pristicladodus, M‘Coy, 
have one characteristic common to both, the central cusp is deeply serrate on each 
side, butinthe amended descriptionsgiven by St. Johnand Worthen (“ Ilinois,” Vol. VI., 
p. 254), and indicated above, the lateral edges of the central cusps of the teeth in- 
cluded in the latter genus are “more or less distinctly undulated or simple,” and 
the only species described, P. springeri is possessed of lateral cusps which are larger 
than the central one, and the edges of the central cusp are smooth. This divergence 
of characters warrant the doubts expressed by the authors as to the relationship of 
the specimens, and leads to the conclusion that they must be excluded from the 
genus Pristicladodus as defined by M‘Coy. 
Carcharopsis colei, Davis. 
(Pl. XLIX., fig. 26.) 
Tooth, length -9 inch, breadth near the base 45 inch, transversely elliptical or 
ovate in section, the lateral diameter being about twice that of the postero-anterior 
diameter. Broadest near the base, the tooth converges gradually to form an 
accuminate apex, curving slightly to one side, and has a generally triangular form ; 
anterior surface of the crown, transversely convex, longitudinally, along the median 
line, nearly straight, curving slightly towards the apex : at the basal extremity the 
TRANS, ROY. DUB. 80C., N.S., VOL. I, 3Q 
