On the Fossil Fishes of the Carboniferous Limestone Series of Great Britain. 425 
whether consisting of a single ridge or more cannot be distinguished ; it is much 
convoluted, its curvature being considerably more than a semi-circle. The two 
anterior teeth, which occupied a position on each side the median suture of the 
jaw, were about half the size of the second teeth, and appear to have been some- 
what similar in form ; they are not sufficiently well preserved to afford any details 
as to form or other characters. 
The surface of the tooth is thickly covered with enamel, through which the denti- 
gerous canals ascend from the bony substratum below, and cause the surface to present 
a punctate appearance. The base or root of the tooth is thick, strong, and osseous, a 
concavity, not so deep as the surface convexity, extends along the central axis of the 
tooth. In this concavity Prof. M‘Coy records ana figures a section of a specimen 
(Brit. Palzeoz. Foss. pl. 3 H, fig. 19, and pl. 3 I, fig. 28), showing what is supposed to 
be a young tooth, exactly concentric with the old one in outline, and presenting a 
similar structure in section. He infers from this a vertical mode of succession of 
the teeth. Several teeth of this genus, in the Enniskillen collection, exhibit 
sections in various directions, but the appearance described by Prof. M‘Coy is not 
presented in any instance even in the largest specimens. It is perhaps more 
probable, considering the inrolled or convoluted character of the teeth and the 
massive thickness of their bony base, that the teeth were constantly or periodically 
enlarged by a growth along their posterior or inside margin. Evidence supporting 
this view is afforded by the fact, that as the teeth increase in size the ridges and 
intermediate depressions radiate with always increasing breadth from the con- 
voluted anterior margin, and at the same time the tooth increases greatly in 
thickness, and further, the anterior part of the tooth is most worn, whilst the 
recently formed posterior surface not having been used to the same extent shows 
very little sign of attrition. 
An example is represented in P]. LIIL, fig. 4, which exhibits a portion of the 
jaw preserved along with the teeth of the right side of the jaw and part of the 
tooth of the left side. The portion preserved represents a wide expansion from 
the teeth inwards, deeply concave, apparently having formed a firm base to this 
part of the palate. Prof. Owen speaking of this specimen (‘Geol. Mag.,” Vol. IV., 
p. 62) says, “The symphysis of the jaw was shorter and the rami met there ata 
more open angle in Streblodus than in Cochliodus; the anterior ends of the last 
crushing teeth come into contact at the back part of the symphysis.” The 
specimen is from Armagh, and forms part of the Enniskillen collection. 
Formation and locality ; Mountain Limestone, Armagh. 
Hex. coll. Earl of Enniskillen. 
Streblodus colei, Agass. (MSS.) 
(Pl. LIL, figs. 5, 6.) 
Streblodus colei.—L, Agassiz, 1859. “MSS. Enniskillen Coll.,” 
5 i Morris & Roberts, 1862. “Quart. Journ. Geol. Soc.,” Vol. XVI Dh, fa, LOI, 
3 ‘ Enniskillen, 1869. “Cat. Foss. Fishes,” p. 8. 
EK % J. J. Bigsby, 1878. “Thesaurus Devonico-Carb.,” p. 365. 
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