4 The Ganoids 
group, while others have shown that the Ostracophori and Arthro- 
dira should be placed far from the garpike in systematic classi- 
fication. Cope, Woodward, Hay, and others have dropped the 
name Ganoid altogether as productive of confusion through 
the many meanings attached to it. Others have kept it as 
a convenient group name for the orders of archaic Actinoptert. 
For these varied and more or less divergent forms it seems con- 
venient to retain it. As an adjective ‘‘ganoid’’ is sometimes 
used as descriptive of bony plates or enameled scales, some- 
in the sense of archaic, as applied to fishes. 
Are the Ganoids a Natural Group ?— Several writers have 
urged that the Ganozdet, even as thus restricted, should not be 
considered as a natural group, whether subclass, order, or group 
of orders. The reasons for this view in brief are the following: 
1. The group is heterogeneous. The Amzde differ more 
from the other Ganoids than they do from the herring-like 
Teleosts. The garpikes, sturgeons, paddle-fishes likewise di- 
verge widely from each other and from the Palgoniscide and 
the Platysomide. Each of the living families represents the 
residue or culmination of a long series, in some cases advancing, 
as in the case of the bowfin, sometimes perhaps degenerating, 
as in the case of the sturgeons. 
2. Of the traits possessed in common by these forms, several 
(the cellular air-bladder, the many valves in the heart, the 
spiral valve in the intestine, the heterocercal tail) are all pos- 
sessed in greater or less degree by certain Isospondyli or allies 
of the herring. All these characters are still better developed 
in Crossoptergyi and Dipneusti, and each one disappears by 
degrees. Of the characters drawn from the soft parts we can 
know nothing so far as the extinct Ganoids are concerned. 
3. The optic chiasma, thus far characteristic of Ganoids 
as distinct from Teleosts, may have no great value. It is urged 
that in closely related species of lizards some have the optic 
chiasma and others do not. This, however, proves nothing 
as to the value of the same character among fishes. 
4. The transition from Ganoids to Teleosts is of much the 
same character as the transition from spiny-rayed to soft- 
rayed fishes, or that from fishes with a duct to the air-bladder 
to those without such duct. 
