628 J. W. DAVIS ON REMAINS OF FOSSIL FISHES 
form of the root, in some measure appears to make it a connecting 
link between Lophodus and Polyrhizodus. It presents the ap- 
pearance of a flat plate, from which rise a number of small columns 
supporting the crown. ‘The small columns being connected at their 
extremities distinguish it from Polyrhizodus. 
This species in form seems to approach Helodus (?) gibbosus, 
N. and W., from the Keokuk limestone of Illinois (Paleontology 
of Illinois, vol. ii. p. 79, pl. v. fig. 3). It may be distinguished, 
however, by the absence of the conspicuous conical gibbosity pro- 
truding on one side opposite the highest point, which characterizes 
the American species ; the latter has also a much deeper base, which, 
though coarse and porous, does not .present the peculiar columnar 
appearance seen in L. conicus. 
LoprHopus sirurcatus, Davis, l. c. p. 408, pl. li. fig. 25 (1882). 
(Plate XX VII. figs. 5, 5 a.) 
LopHopus ancuLARIs, Davis, sp.n. (Plate XXVII. fig. 25.) 
Teeth. Subpyramidal in outline; diameter across the base 0°8 
inch; height of crown from base-line 0:45 inch. Crown 0:2 inch 
wide antero-posteriorly ; central portion forming an acutely pointed 
triangular apex; the major portion equally and rapidly depressed 
on each side, but towards the lateral extremities extending almost 
horizontally, and ending in an obtusely angular point. From 
the apex an acutely angular projection of the coronal surface forms 
a carina, situated slightly anteriorly to the median line; anterior 
and posterior margins prominent, slightly rounded, and more or 
less corrugated, especially towards the extremities. The corru- 
gations occasionally extend upwards towards the submedian carina, 
those on the posterior surface being inclined diagonally between 
the base and the apex. Surface smooth and polished, with minute 
pittings. Base apparently small, mostly hidden in the matrix, 
but, like the tooth, deeply concave. 
The characters pertaining to this tooth distinguish it readily from 
all the hitherto described species of Lophodus. 
Genus Drttoprycuius, Agass. MSS. ; 
Davis, Trans. Roy. Dubl. Soc. n. s. vol. i. p. 482 (1882). 
DELTOPTYCHIUS PLICATUS, Davis, sp.n. (Plate XXVI. figs. 13, 14.) 
Teeth. Of upper jaw (Plate X XVI. fig. 14) subtriangular in out- 
line; convoluted, expanding radially from the inside of the jaw 
outwards; greatest diameter 0°8 inch. Surface raised in central 
part, forming a large and prominent median ridge, widening as it 
approaches the outer margin of the tooth. Anterior ridge separated 
by a wide sulcus from the central one. It is narrow, but well- 
developed, and marks the point of contact between the teeth on 
each ramus of the jaw. The posterior ridge, coinciding with the 
posterior margin, is most divergent from the central axis of the 
tooth ; it is comparatively small, and separated from the central 
