404 
DAVIS : HETEROLEPIDOTUS. 
cranial bones have disappeared ; the lower portion of the head 
IS however preserved. The larger part of the tail is also wanting ; 
the dorsal fin is well preserved ; and the outline of the body clearly 
indicated, the latter gracefully fusiform. The length from the tip of 
the snout to the base of the tail is about 13 inches, to which must 
be added 3 inches for the tail ; the imperfect state of the head rend- 
ers its exact length slightly uncertain, but of the length named, the 
head probably occupied 4 inches. The greatest depth of the body is 
between the dorsal and ventral surfaces, immediately behind the 
pectoral fin where it is 4 inches ; from this diameter the body tapers 
gradually backwards to about 1 -5 inch at the base of the tail. 
The head was probably large ; the parts preserved comprise the 
upper and lower jaws, a number of branchiostegal plates, and some 
bones of the cranium. The part of the upper jaw preserved is an 
inch in length ; broad posteriorly, but rapidly tapering to a more or 
less acuminate termination anteriorly; it contains 16 or 18 teeth 
uniform in size, 0*6 of an inch in length, conical in form, pointed, 
and slightly curved inwards. The lower jaw is similarly armed to 
the upper one. The exposed branchiostegal plates or rays are 18 in 
number ; the largest is 1-5 inches in length, and -15 in breadth, they 
diminish in size towards the median line, the shortest being -85 of an 
inch in length. There were probably 12 or 14 rays on each side, in 
this specimen it is difficult to determine where the median line was, 
the rays from the opposite side being exhibited in close contact with 
those on the more exposed one. The plates are flat, imbricating, 
smooth, and covered with glistening enamel. Parts of other bones, 
enamelled and more or less pustulate are also preserved, but not so 
well as to be easily identified. 
The scales are large, thick, more or less rhomboidal in outline, 
covered with ganoine and frequently shewing concentric lines of 
growth; those on the anterior median portion of the body are serrated 
along the posterior margin as shown in the enlarged drawing of a 
scale taken from the laternal line about 2 inches behind the head 
(pi. XXII., fig. la.) The scales midway between the dorsal and ventral 
surfaces of the body are largest, the exposed part of the scale being 
equal in height to the length, an additional portion, equal to one- 
