On the Fossil Fishes of the Carboniferous Limestone Series of Great Britain. 433 
descriptions there is no distinct evidence of there having been more than a single 
tooth to each ramus of the jaw. It is possible, nevertheless, that, as in the case of 
Streblodus, there may have been smaller teeth situated in a position anterior to 
those of the lower jaw, and it may be well to withhold a firm opinion on the subject 
until further negative or affirmative evidence shall have been adduced from future 
discoveries. 
The genus Deltoptychius differs from Cochliodus in the prominence and indivi- 
duality of its ridges, especially the median and anterior ones, and the deeply 
concave sulcus separating them. The median ridge in the former extends much 
more obliquely across the surface of the crown, causing the posterior margin to 
assume a broader expansion than in Cochliodus. 
Deltoptychius acutus, Agass., MSS. 
(PL, INU, ties, US=1 7/5) 
Cochliodus acutus— L. Agassiz, 1838. ‘Rech. Poiss. Foss.,” Vol. LIL, p. 174, indet. 
5 J. E. Portlock, 1843. “Geol. Report of Londonderry, &e.,” p. 466. 
3 3 C. G. Giebel, 1848. “Fauna der Vorwelt,” Vol. L, pt. 3, p. 336. 
9 7 H. G. Bronn, 1848. ‘ Nomencl. Palont.,” p. 317. 
9 5 - 1849. ‘Enumerator Paleont.,” p. 647. 
y 5 J. Morris, 1854. “Catal. Brit. Foss.,” p. 322. 
on Ae F. J. Pictet, 1854. “Traité de Paléont.,” Vol. IL., p. 267. 
3 . F. M‘Coy, 1855. “ Brit. Paleoz. Foss.,” p. 621, Pl. 3 I., fig. 24. 
Deltoptychius acutus—-L. Agassiz, 1859. “MSS. Enniskillen Coll.” 
5 - Morris & Roberts, 1862. “Quart. Journ. Geol. Soc.,” Vol. XVITI., p. 100. 
Yochlioduscompactus—R. Owen, ~ 1867. “Geol. Mag.,” Vol. 1V., p. 59, Pl. IV., fig. I. 
Deltoptychius acutus—Enniskillen, 1869. “Catal. Types Foss. Fishes,” p. 4. 
Cochliodus acutus - Young & Armstrong, 1871. “Trans. Geol. Soc., Glasgow,” Vol. III., spt., p. 69. 
Deltoptychius acutus—Armstrong, Young, 1876. “Catal. W. Scot. Foss.,” p. 61 
and Robertson, ; SN AIT A ie aE a 
J. J. Bigsby, 1878. ‘“Thes. Dev. Carb.,” p. 353. 
2? 9? 
Prof, M‘Coy describes the teeth as follows—“ Posterior teoth, oblong, obliquely 
attenuated behind at an angle of about 65°; anterior edge sloped backwards and 
inwards at about 60°; surface with three very strongly marked, oblique ridges, 
separated by deep concavities; the first ridge most prominent, narrow, acutely 
angulated, coinciding with the anterior edge, which is very deeply sloped, usually 
separated from the adjoining concavity by an obscure narrow sulcus; middle ridge 
much broader and placed rather behind the middle of the tooth, sloping gradualiy 
towards the base of the anterior ridge, but abruptly rounded into the deeper and 
narrower concavity, which separates it from the posterior marginal ridge which is 
prominent, narrow, and rounded, forming the posterior point of the tooth. Middle 
tooth unknown. Anterior tooth, small triangular, marked with three narrow 
prominent, very oblique ridges, the first coinciding with the posterior margin, and 
3 Y¥ 2 
