On the Fossil Fishes of the Carboniferous Limestone Series of Great Britain. 518 
Teeth ; “ Wide, much compressed, upper cutting edge having a gentle but 
variable convexity ; usually divided mto about thirty rounded notches, or obtuse 
pointed denticles, slightly larger in the middle than at the ends, and from between 
each pair of which a more or less distinct sulcus extends towards the base of the crown, 
rarely reaching more than halfway, and forming a fringe-like plication, and some- 
times nearly obselete; apices of the denticles minutely crenulated under the lens ; 
front surface of crown flat, highly polished, sloping outwards, and terminating in an 
obtuse angle in the middle, and directed downwards and outwards; the very 
prominent base of the crown being surrounded by three or four flat imbricating 
bands of ganoine; root abruptly flattened, also narrower than the crown, and 
about equalling it in depth.”—M‘Coy. The posterior surface of the crown is deeply 
concave, smooth in the central part, plications at base of crown prominent, extending 
with considerable convexity towards the base and much lower than on the anterior 
surface. Coronal margin minutely serrated corresponding with the minor crenula- 
tions of the anterior surface, but the larger obtusely denticulated groups are not 
represented on the posterior face. Breadth of crown about ‘8 of an inch ; height of 
crown anteriorly °3 inch; root one-third longer than the crown ; posteriorly the 
crown is higher than the depth of the root. 
Formation and locality : Mountain Limestone, Armagh. 
Hex coll. The Ear] of Enniskillen. 
Ctenopetalus crenatus, Davis. 
(BE DXa fies! 9) 9a,:9d:) 
Teeth, small, 4 of an inch across the crown, and ‘25 inch in height. Crown, 
anteriorly slightly convex between the lateral extremities ; cutting edge slightly 
rounded, and divided into a number of minute denticles, smooth, obtusely-rounded, 
without minor division, which distinguishes them from C. serratus. Enamelled 
Surface ot the crown bounded below by several plicated folds of ganoine, the upper 
one enveloping the base of the crown. Lateral extremities of the front face acum- 
inate, expanding towards the centre, which descends over the root with a promi- 
nently-advanced acute point. Posterior surface of crown concave, descending to 
nearly twice the depth of the anterior one, towards the root. Five or six broadly 
expanded plications occupy the base; root narrow, thin, anteriorly much con- 
tracted. 
This beautiful little species possesses all the generic characters of Ctenopetalus, 
but is different in several respects from the type species C. serratus of Agassiz. It is 
less robust ; the median portion of the anterior face of the crown forms an acute point, 
which in C’ serratusis rounded and obtuse, and the apices of the denticles are smooth 
and undivided. ‘This species bears a considerable resemblance to C. medius, from 
the Chester Limestone, Illinois (“ Palezont. Illinois,” Vol, VI., p. 400), but is dis- 
tinguished by the pointed apex of the crown in the latter, by each denticle having 
412 
