The Ganoids 253 
Order Chondrosteii—The order Chondrostet (yorvdpos, carti- 
lage; ooreor, bone), as accepted by Woodward, is characterized 
by the persistence of the notochord in greater or less degree, 
the endoskeleton remaining cartilaginous. In all, the axonosts 
and baseosts of the median fins are arranged in simple regu- 
lar series and the rays are more numerous than the sup- 
porting elements. The shoulder-girdle has a pair of infra- 
clavicular plates. The pelvic fins have well-developed base- 
osts. The branchiostegals are few or wanting. In the living 
forms, and probably in all others, a matter which can never 
be ascertained, the optic nerves are not decussating, but form 
an optic chiasma, and the intestine is provided with a spiral 
valve. In all the species there is one dorsal and one anal fin, 
separate from the caudal. The teeth are small or wanting, 
the body naked or covered with bony plates; the caudal fin is 
usually heterocercal, and on the tail are rhombic plates. To 
this order, as thus defined, about half of the extinct Ganoids 
belong, as well as the modern degenerate forms known as stur- 
geons and perhaps the paddle-fishes, which are apparently derived 
from fishes with rhombic enameled scales. The species extend 
from the Upper Carboniferous to the present time, being most 
numerous in the Triassic. 
At this point in Woodward’s system diverges a descending 
series, characterized as a whole by imperfect squamation and 
elongate form, this leading through the synthetic type of Chon- 
drosteide to the modern sturgeon and paddle-fish, which are 
regarded as degenerate types. 
The family of Saurorhynchide contains pike-like forms, with 
long jaws, and long conical teeth set wide apart. The tail is 
not heterocercal, but short-diphycercal; the bones of the head 
are covered with enamel, and those of the roof of the skull form 
a continuous shield. The opercular apparatus is much reduced, 
and there are no branchiostegals. The fins are all small, without 
fulcra, and the skin has isolated longitudinal series of bony 
scutes, but is not covered with continuous scales. The principal 
genus is Saurorhynchus (=Belonorhynchus; the former being 
the earlier name) from the Triassic. Sawrorhynchus acutus from 
the English Triassic is the best known species. 
The family of Chondrosteide includes the Triassic precursors 
