GANOIDS, 
5 IG 
( Dapediidce ) is represented by Dapedius, Lepidotus, and several other allied 
genera, in which the body is more or less deeply fusiform, the suspensory apparatus 
of the lower jaw either vertical or inclined forwards, the cleft of the mouth narrow, 
the teeth cylindrical or in the form of button-like knobs, the vertebrae not more 
than rings, and the 
dorsal fin not ex¬ 
tending more than 
half the length of 
the body. In this 
family the teeth 
have vertical suc¬ 
cessors ; and while 
some of the earlier 
THE GIANT SCALE-TOOTH, WITH A DETACHED SCALE AND TEETH genera date fl’Om 
(much reduced). the Trias, the scale- 
tooths ( Lepidotus ), of which an example is figured in the illustration, survived till 
the Chalk. Some of the species of this genus attained very large dimensions ; and 
their remains are beautifully preserved in the Lithographic Limestone of Bavaria. 
In all these the scales are of the typical quadrangular ganoid type. 
The Sturgeon-Tribe, —Suborder Chondrostei. 
This important suborder brings us to the last group of the fan-finned fishes 
(Actinopterygii), which forms a division by itself differing in several important 
particulars from the one including the whole of the foregoing suborders ; the more 
important characters of the first division having been given on p. 334. Whereas 
in that division the number of dermal rays in the dorsal and anal fins is equal to 
the supporting elements in the true internal skeleton, in the present division the 
dermal rays are more numerous than their supports. Then, again, whereas in the 
former division the pelvic fins have their superior row of supporting ossicles, or 
baseosts, ruclimental or wanting, in the present group these are well developed. 
The living representatives of the sturgeon tribe agree with the bow-fish and its 
allies in the want of any interlacing of the fibres of the optic nerves at their crossing, 
and likewise in the presence of a spiral valve to the intestine. In both the living 
and extinct types the tail is of either the diphycercal or heterocercal type. As a 
suborder, the sturgeon tribe may be characterised by the more or less completely 
persistent notochord, by the inferior and superior supporting ossicles (axonosts and 
baseosts) of the dorsal and anal fins forming a simple and regular series, and also 
by the presence of a pair of infraclavicular plates in the pectoral girdle. In all 
the known forms there is a single dorsal and anal fin, both of which are well 
separated from the caudal; while in the existing members the air-bladder is fur¬ 
nished with a duct. Although represented at the present solely by the sturgeons 
and their allies, the group was very abundant during the Secondary epoch ; and 
whereas the sturgeons, together with certain extinct families, form what may be 
termed a degenerate specialised series characterised by the absence of ganoid scales 
in a second and normal series the body was covered with such scales. 
