FROM THE YOREDALE SERIES. 627 
contrary, much compressed antero-posteriorly. The section in that 
direction is acutely pointed. 
No specimen has hitherto occurred which has exhibited the basal 
portion of the tooth with sufficient clearness for description, but it 
appears to be thin and not very deep. 
Lopnopts tzvis, Davis, l. c. p. 409, pl. li. figs. 26, 27 (1882). 
The specimens from the Leyburn limestone are similar to those 
obtained lower down in the stratigraphical series. The surface is 
covered with deeper puncte, and does not present quite so smooth 
an appearance. In rare instances from two to four or five teeth 
have been found connected; and a mass of what may be fossilized 
cartilage has been found attached to the base of one such group. 
This species approaches Lophodus mammillaris, Ag., in contour ; 
but is easily distinguished by its smaller size, and by the absence of 
the two small tuberosities, one before and the other behind the basal 
portion of the median cone, which Prof. de Koninck considers 
the distinguishing characteristic of L. mammiliaris. From Lophodus 
didymus, Ag., it is separated by the absence of the deep notch or 
groove in the apex of the median cone. 
LopHopvs serratus, Davis, l. c. p. 408, pl. li. figs. 23, 24 (1882). 
(Plate XXVII. fig. 19.) 
This species is distinguished from Lophodus laevis by the tuber- 
culated apex of the crown, which also separates it from LZ. mam- 
millaris. It is also more angular and graceful in appearance than 
L. levis. 
LopHopvs conicus, Davis, sp.n. (Plate XXVI. fig. 18.) 
Teeth. Small, transverse diameter 0-4 inch; antero-posterior 
diameter 0-1 inch; height of crown 0-1, and depth of base 0:05 
inch. Crown, central portion rounded, prominent, gibbous, bend- 
ing slightly from the centre towards one extremity. Lateral 
extension of the coronal surface in the same direction rapidly de- 
pressed from central cone, rounded antero-posteriorly, and termi- 
nating abruptly. On the cpposite side, the lateral extension of the 
crown slopes gradually from the summit of the central cone to the 
base, with which it forms an acute angle. Surface uniformly 
punctate. Base equal in extent with the crown; composed of a 
considerable number of small rootlets, separated by vertical inter- 
stices, extending from the junction with the crown to the bottom of 
the root, where the whole of the rootlets are connected together by a 
lateral extension of their substance. 
The crown in this species bears some resemblance to that of Zo- 
phodus levissimus, Ag., except that itis narrower from back to front, 
and that its subcentral cone is more prominent, and is bent over to one 
side considerably more than any of the specimens hitherto observed, 
belonging to that species. The great difference which distinguishes 
it from all other British species hitherto described, the peculiar 
