On the Fossil Fishes of the Carboniferous Limestone Series of Great Britain. 515 
convex, lower part thick and strong; crest slightly arched or straight, divided 
into about seven denticulations, large, broad at the base, laterally thin, and 
obtusely pointed; lateral denticles slightly smaller than those of the centre. The 
denticles divide the crown to one-half its depth, and between each the line of divi- 
sion is continued, forming a sulcus extending almost to the base of the crown. The 
latter is prominent, and forms a single broad fold or ridge extending across the 
anterior coronal surface, and on each side bending downwards, and thence enyelop- 
ing the posterior surface of the crown. Posterior surface is concave laterally, and 
extends one-third lower from the apex than the anterior surface. Surface of crown 
is thickly enveloped with ganoine of a particularly hard and dense character, espe- 
cially near the apex or crest. Base proportionately thick and strong, narrower 
than crown ; anterior surface contiguous to crown much depressed for about one- 
third its vertical extent; below this the base is tumid, prominent, rounded and 
thick, fibrous, and close in structure. 
Formation and locality: Mountain Limestone, Armagh. 
Ex. coll. Earl of Enniskillen. 
Harpacodus clavatus, Davis. 
(IPL Id, sie, 2X0,)) 
Teeth, small and delicate, *1 inch in height, and ‘25 inch. broad. Crown, 
circular, base and apex, sub-parallel. Cutting edge divided into eight minute 
rounded, clavate, obtusely pointed denticles, coated with glistenmg enamel, 
diminishing with an extremely slight gradation in size towards each lateral 
extremity. The denticles occupy more than one-half the surface of the crown. 
Base of crown is imperfect, but was somewhat prominent, and apparently a fold of 
the ganoine separated it from the root. Posterior surface not visible. Root very 
short, conforming to the generally circular form of the crown—thick from back to 
front, and somewhat produced downwards at each end. 
This species differs from Harpacodus dentatus, Ag., in its broad circular form and 
short low crown. The denticles are greater in number, well-defined, with a clavate, 
rounded extremity, those of H.dentatus being broader at the base, thin, with a laterally 
obtuse point. The base of this species is also quite distinct from that of /7. dentatus, 
for whilst the latter is boldly prominent with a well-rounded tumid root, 7. clavatus 
has a very short root, thick and widely expanded, and whilst it possesses the 
appearance of being perfect, it differs so much from the type specimen in this 
respect that it may be possible that a part of the root has been broken away. 
Formation and locality : Mountain Limestone, Armagh. Unique specimen. 
He coll. Karl of Enniskillen. 
