On the Fossil Fishes of the Carboniferous Limestone Series of Great Britain 471 
Mesogomphus lingua, Agass. (MSS.) 
(Pl. LVIIL, fig. 16.) 
Mesogomphus lingua—L. Agassiz, 1859. MSS., Enniskillen Collection. 
55 * Morris and Roberts, 1862. ‘ Quart. Journ. Geol. Soc.,’ Vol. XVIIL., p. 101 
“a a Enniskillen, 1869. ‘Catal. Type Specimens,” p. 6. 
7 5s J. J. Bigsby, 1878. ‘Thes. Devonico-Carb.,” p. 359. 
Teeth, General form, as indicated by the specific name, is tengue-shaped. 
Length along the median axis ‘9 of an inch, greatest breadth at posterior portion is 
the same as the length. The breadth gradually diminishes to the front, ending in 
a rounded anterior extremity. Crown slightly convex in each direction ; lateral 
borders raised; anterior portion considerably worn by attrition, especially near 
the extremity. From the centre of the crown backwards the surface is depressed 
towards the middle of the posterior margin, and a well-defined semi-circular suture 
like depression extends from the posterior margin towards the centre ; the portion 
of the crown separated by this suture, occupies rather more than the central third 
of the margin, and extends ‘25 of an inch over the coronal surface, it is marked by 
two or three transverse ridges extending across its surface; the whole surface of 
the crown is minutely punctate. Anterior termination circular, gradually expanding 
laterally towards the posterior margin, which is convex. Postero-lateral angles 
obtusely rounded. Base thickest in the middle, thinner towards each side ; from 
the posterior to the anterior extremities about the same thickness is maintained ; 
the form of the base is the counterpart of that of the crown. The enamel of the 
crown projects anteriorly above the base, whilst posteriorly the base extends beyond 
the crown, especially at each of the postero-lateral angles. 
Formation and locality : Carboniferous Limestone, Armagh. 
Ex. coll, Earl of Enniskillen. 
Genus.—Pleurogomphus, Agass. (MSS.) 
Pleurogomphus—L. Agassiz, 1859. MSS., Enniskillen Collection. 
Palatal teeth: outline sub-quadrate, medium size, length and _ breadth 
equal. Crown, concave, lateral borders slightly prominent, surface uniformly 
punctate ; posterior third of coronal surface depressed, lateral third on each side 
separated by deep sulci or sutures. Anterior margin obtusely rounded, lateral and 
posterior margins straight. Postero-lateral angles produced acutely. Base thick, 
striated, longitudinally concave ; transversely convex extending slightly beyond the 
fateral margin of crown ; anteriorly and posteriorly shorter than crown. 
In some respects Pleurogomphus bears a resemblance to Copcodus cornutus, it has 
the closely approximating outline of the coronal surface, but that of the base is 
quite different ; in the latter the base is produced to form largely extended postero- 
TRANS. ROY DUB. SOC., N.S., VOL. I. 4D 
