406 
DAVIS : HETEROLEPIDOTUS. 
should have strong interDal support. The number of rays cannot be 
determined. 
The anal Jin was large and powerful. It is imperfect, but 
sufficient is preserved to shew that the rays were thicker though 
shorter than those of the pectoral or ventral fins ; the longest ray is 
onl}^ preserved to the extent of -75 of an inch, of this -5 of an inch 
at the base is smooth with a single longitudinal groove, the remain- 
ing portion being composed of closely jointed ossicles. 
The candal fin is partially preserved, the whole of the lower 
lobe of the fin has been broken off and lost during the extraction of 
the specimen from the matrix. From the portion preserved, it 
appears that there was a prolongation of the vertebrae to the upper 
lobe but to what extent is not exactly defined. A number of 
strong, pointed, imbricating scales, envelope the base of the tail on 
the dorsal surface, and were continued some distance along the 
margin of the fin. The rays forming the upper lobe of the tail are 
strong at the base, consisting of ossicles equal in length to their 
breadth, attached by transverse articulations ; at about -8 of an inch 
from the base they dichtomize, each branch being again divided. 
Sir Phihp de Malpas Grey Egerton in the XIII Decade of the 
Geological Survey, separated two species described by Prof. Agassiz 
as Lepidotus fimbriatus and L. serrulatus, and constituted for them a 
new genus which he named Heterolepidotus. They differ essentially 
in two particulars from the typical Lepidoti and approach the Sauroid 
family Eugnathus. The differences are in the characters of the 
teeth, and the scales of the ventral surface of the body. The teeth 
in the true Lepidoti are either large and round like the tritorial teeth 
of the Pycnodonti, or obtusely conical and uniform in size ; in 
Heterolepidotus they are sharp and elongated, of various sizes and 
very numerous. The scales of Lepidotus are uniform, or nearly so 
in size, over the whole surface of the body, whilst in Heterolepidotus 
they are considerably elongated and narrow on the under side of the 
body, resembling those of Eugnathus. The species now described 
appears to have a somewhat contracted gape, and the teeth are shorty 
conical and uniform, and in these respects it approaches the characters 
of the true Lepidoti. The scales on the other hand resemble those 
