The Ganoids ¥ 
Admitting all this, it is nevertheless natural and convenient 
to retain the Ganoidei (or Chrondrostet if the older name be 
discarded on account of the many meanings attached to it) 
as a group equivalent to that of Tcleostei within the class or 
subclass of Actinopteri. It comprises the transitional forms 
between the Crossopterygii and the bony fishes, and its members 
are especially characteristic of the Mesozoic age, ranging from 
the Devonian to the present era. 
Of the extensive discussion relating to this important ques- 
tion we may quote two arguments for the retention of the sub- 
class of Ganoids, the first by Francis M. Balfour and William 
Kitchen Parker, the second from the pen of Theodore Gill. 
Balfour and Parker (‘‘ Structure and Development of Lepi- 
dosteus,” pp. 430-433) thus discuss the 
Systematic Position of Lepidosteus.—‘‘ Alexander Agassiz con- 
cludes his memoir on the development of Lepidosteus by point- 
ing out that in spite of certain affinities in other directions 
this form is ‘not so far removed from the bony fishes as has 
been supposed.’ Our own observations go far to confirm Agas- 
siz’s opinion. 
“Apart from the complete segmentation, the general de- 
velopment of Leptdosteus is strikingly Teleostean. In addition 
to the general Teleostean features of the embryo and larva, 
which can only be appreciated by those who have had an oppor- 
tunity of practically working at the subject, we may point to 
the following developmental features * as indicative of Teleos- 
tean affinities: 
““(1) The formatica of the nervous system as a solid keel 
of the epiblast. 
‘““(2) The division of the epiblast into a nervous and epi- 
dermic stratum. 
‘“(3) The mode of development of the gut. 
‘“(4) The mode of development of the pronephros; though 
the pronephros of Lepidosteus has primitive characters not 
retained by Teleostei. 
“(s) The early stages in the development of the vertebral 
column. 
* The features enumerated above are not in all cases confined to Lepidos- 
teus and Teleostei, but are always eminently characteristic of the latter. 
