626 BRITISH PALAZOZOIC FOSSILS. [ Pisces. 
of them thinning out above at irregular distances, other pairs uniting branchwise into one above, some 
appearing to taper to both ends; most of the ridges are nearly smooth in a great part of their course, or 
shewing a more or less distinct crenulation on their sides (about three in the space of one line), from small 
opposite lateral tubercles; in certain irregular spots these lateral tubercles increase in size and strength, and 
distinctly cross the ridges, by becoming connected across them; in several of the ridges, particularly towards 
the base, the transverse tuberculation and notching becomes so distinct, that the ridge is separated into a 
row of triangular tubercles, about half a line long. 
The extreme irregularity of the ridges of this species, no two of them being quite alike, and several 
of them totally changing their aspect after short distances, easily distinguish this species from its congeners. 
The finely striated base is of rather small size, and rapidly tapering, the line of separation between it and 
the ridged exterior being very oblique. 
Position and Locality —Rare in the lower carboniferous limestone of Armagh. 
Explanation of Figures—PI. 3. 1. fig. 32, fragment of base natural size, shewing part of the base of 
insertion and commencement of ridging, with few tubercles; fig. 33 ditto, fragment near middle, shewing 
the irregular character of the ridging and tuberculation; fig. 33 a, portion of surface of last specimen, 
magnified; fig. 33 6, ditto section, shewing the broad ridge of anterior face. 
Genus. CTENOPTYCHIUS (4g.) 
Gen. Char.—Teeth small, highly polished, strongly compressed, rounded or obtusely pointed, edge divided 
into several strong denticulations; base of crown with a few imbricating folds of ganoine; bony root oblong, 
flattened in the same direction as the crown. 
This genus differs from Petalodus chiefly in its larger denticles of the edge. 
It is found in the Devonian and carboniferous rocks. 
CTENOPTYCHIUS APICALIS (Ag.) 
Ref, and Syn. = C. apicalis Ag. Poiss. Foss. t.19. f. 1. and Binney, Trans. Manch. Geol. Soe. Vol. I. t. 5. f. 19. 
= Petalodus dentatus Ow. Odont. p. 62. = Cten. macrodus Ag. name in lists, and Portk. Geol. Rep. 
tat. 7 
Desc.—Crown transversely oval, thick, highly polished ; upper edge semielliptically rounded, divided into 
six or seven very thick, elliptically pointed lobes, diminishing rapidly in size to the exterior one on each side, 
which is very small, the largest tooth being usually a little one side of the middle, having three denticles on 
one side, and four on the other, regularly diminishing in size from the central one; imbricating fold of ganoine 
at base of crown gently arched downwards, single or double, forming the most prominent part of the profile 
of the tooth, the surface sloping with slight convexity to the cutting edge above, abruptly depressed to the 
dull, bony, root below; the root about as deep as the crown is high, fibrous, but much thinner than the crown. 
When well preserved the surface of the crown is smooth. Average width of moderate-sized specimen four lines, 
greatest height of crown two and half lines, depth of root the same, width of root about three and half lines. 
The names C. macrodus Ag. and P. dentatus Owen were applied to the same specimens in Capt. Jones’s 
collection, and I am perfectly satisfied of their identity with C. apicalis; the Irish specimens having quite as 
near an approximation to a median point as the English ones. 
Position and Locality —Not very uncommon in the carboniferous limestone of Armagh. 
CTENOPTYCHUS SERRATUS (Ow.) PI. 3.1. fig. 21, 22, 23. 
Ref—Owen Odontog. p. 62. 
Desc.—Tooth wide, much compressed, upper cutting edge having a gentle but variable convexity ; usually 
divided into 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 half way, and forming a fringe-like plication, and sometimes nearly 
obsolete ; apices of the denticles minutely crenulated under the lens; front surface of crown flat, highly polished, 
