The Ganoids 249 
group, while others have shown that the Ostracophori and Arthro- 
dtra 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. 
Classification of Ganoids.— The. subdivision of the series 
of Ganoidei into orders offers great difficulty from the fact 
of the varying relationships of the members of the group 
and the fact that the great majority of the species are 
known only from broken skeletons preserved in the rocks, 
It is apparently easy to separate those with cartilaginous 
skeletons from those with these bones more or less ossified. It 
is also easy to separate those with bony scales or plates from 
those having the scales cycloid. But the one type of skeleton 
grades into the other, and there is a bony basis even to the 
thinnest of scales found in this group. Among the multitude 
of names and divisions proposed we may recognize six orders, 
for which the names Lysoptert, Chondroste1, Selachostomz, 
Pycnodonti, Lepidostet, and Halecomorphi are not inappropriate. 
Each of these seems to represent a distinct offshoot from the 
first primitive group. : 
Order Lysopteri—In the most primitive order, called Lysop- 
teri (Avoods, loose; arepor, fin) by Cope, Heterocerci by Zittel 
and Eastman, and the “ascending series of Chondrostei” by 
Woodward, we find the nearest approach to the Chondropter- 
ygians. In this order the arches of the vertebre are more or 
less ossified, the body is more or less short and deep, covered 
with bony dermal plates. The opercular apparatus is well 
developed, with numerous branchiostegals. Infraclavicles are 
present, and the fins provided with fulcra. Dorsal and anal 
fins are present, with rays more numerous than their supports; 
ventral fin with basal supports which are imperfectly ossified ; 
caudal fin mostly heterocercal, the scales mostly rhombic in 
form. All the members of this group are now extinct. 
