5°6 
GANOIDS. 
Sandstone districts of the central counties, and likewise in the chalk streams of the 
south. In the latter area grayling occasionally run to nearly 4 lbs. in weight, 
but in Northern Scandinavia they may reach 1 lb. more. In Switzerland they are 
found in Lake Constance and other large pieces of water. An elegantly-shaped 
fish, the grayling varies considerably in colour according to the season of the year, 
the back being generally greenish brown, passing into grey on the sides, while the 
under-parts are silvery. The sides of the head are yellow, with black spots, which 
also occur on the fore-part of the body; and brownish grey longitudinal stripes 
run in the direction of the rows of scales. The pelvic and anal fins are violet, 
frequently marked with brown crossbars; the pectorals are yellow, turning to red 
in the breeding-season; while the black-bordered dorsal and caudal are generally 
red, although sometimes blue; the former, and sometimes also the latter, being 
ornamented with longitudinal dark bands or rows of spots. A second species, 
with smaller scales, inhabit the mountain streams of Dalmatia, but the other two 
are North American. 
A remarkable fish from the fresh waters of the United States 
known as Percopsis guttata, which has the general characters of a 
salmonoid but the mouth and scales of a perch-like type, is regarded as represent¬ 
ing a family ( Percopsidce ) by itself, nearly allied to the salmon tribe. 
Percopsis. 
The Bony Pike and its Kindred, —Suborder .ZEtheospondyli. 
The remaining groups of the Teleostomous fishes exhibit a more or less decidedly 
lower type of organisation than those described above; and, although the sturgeons 
are still well represented, these groups as a whole are evidently waning ones 
at the present day, having only very few living forms, whereas in past epochs 
some of them formed the dominant types in the fish-fauna of the world. The bony- 
pikes of the fresh waters of North America constitute a family (Lepidosteidce) 
which forms the sole existing representative of a distinct suborder. While 
agreeing with the preceding suborders in the divisional characters mentioned 
on p. 334, the members of this group and the next exhibit much more 
marked differences from all the foregoing groups than do the latter from one 
another. With the exception of the extinct spear-beaks, the'tail is of the 
abbreviated heterocercal type; that is to say, that while its fin is more or less nearly 
symmetrical, the vertebral column, which retains its primitive tapering extremity, 
runs in the upper half. The scales are ganoid, and very frequently quadrangular, 
although they may be rounded and distinctly overlapping. In the living represen¬ 
tatives of both suborders the air-bladder is connected with the oesophagus by a 
duct, in the same manner as in the tube-bladdered fishes; but the optic nerves 
simply cross one another, without any interlacing of their fibres, and there is 
a spiral valve to the intestine. Whereas, with the exception of one extinct 
group of herrings, the whole of the suborders of bony fishes hitherto noticed are 
unknown previous to the Cretaceous epoch, members of the two groups to 
be now considered were abundant in the antecedent Jurassic period. The 
group including the bony-pike may be distinguished from the next by the full 
ossification of the internal skeleton; the scales being always of the typical 
