On the Fossil Fishes of the Carboniferous Limestone Series of Great Britain. 435 
Deltoptychius gibberulus, Agass. MSS. 
(Pl. LIIL., figs. 18-19.) 
Deltoptychius gibberulus—L. Agassiz, 1859. “ MSS. Enniskillen Coll.” 
a es Morris & Roberts, 1862. “ Quart. Journ. Geol. Soc.,” Vol. XVIII., p. 100. 
5 Enniskillen, 1869. “ Catal. Types. Foss. Fishes,” p. 4. 
J. J. Bigsby, 1878. “ Thes. Dey. Carb.” p. 353. 
Teeth of lower jaw, more rhomboidal in outline than in D. acutus, and ridges less 
acutely developed. Surface formed of three ridges with intermediate sulci, first 
ridge corresponding with the antero-lateral or median margin, 1s obtuse and 
rounded, descending at an acute angle to the edge of the tooth ; middle ridge 
broad and gibbous ovcupying a large proportion of the surface of the tooth, and 
much wider than in D. acutus; separated from the anterior ridge by a narrow and 
not very deep sulcus, which towards the anterior extremity is almost obliterated. 
The third ridge is imperfectly preserved, but sufficient remains to show that it was 
broader and more prominent than in .D. acwtus; the sulcus intermediate between 
this and the median ridge is shallow and wide, quite different from the deep and 
narrow concavity of D. acutus. Length, 1:25 inch, median margin ‘7 inch. Teeth 
of upper jaw, sub-triangular in outline, greatest length 1:0 inch, along the antero- 
lateral margin breadth, across posterior margin ‘7 inch, and of the median edge ‘7 
inch. ‘The crown is formed of a large median ridge, and two much smaller and 
less developed ones forming the antero-lateral and posterior margins of the tooth. 
The median ridge is pointed and narrow anteriorly, gradually expanding posteriorly 
into a broadly rounded convexity which occupies the greater part of the coronal 
surface. The depression or sulcus between the median and antero-lateral ridge is 
somewhat deep anteriorly, widely expanded and shallow towards the posterior 
margin; postero-lateral ridge slightly prominent, much less so than in D. acutus ; 
antero-lateral ridge, angular, small, much inferior to the median one in height, inter- 
vening sulcus slight and narrow. This species differs from Deltoptychius acutus in 
the broadly expanded median ridges as compared with the less prominent ones of 
D. acutus, whilst the lateral ridges, acutely prominent in the latter are compara- 
tively small and obtuse in D. gibberulus. The posterior margin of the teeth of the 
upper jaw of D. acutus is convex and rounded, extending considerably beyond the 
antero and postero-lateral angles, whilst in D. gibberulus the margin is almost straight. 
Formation and locality : Mountain Limestone, Bristol. Hook-point, Ireland. 
Hx. coll. Earl of Enniskillen. 
