CONCLUSIONS. 131 



systematic distinction between the pinnate and simple forms), came from 

 an early Megalopieris stock, probably through the alethopteroid forms. 

 The earliest flora, so far as I know, in which any of these occur, that of 

 the Middle Devonian at Saint Johns. New Brunswick, 4 besides contain- 

 ing the Megalopteris daivsoni, has also representatives of Neuropteris, most of 

 which are alethopteroid, and of Alethopteris, including the A. grandis and 

 A. discrepans already referred to. It is not improbable that the three 

 of these genera originated in a common stock ; and since the Megalopteris 

 group offers a comprehensive type from which the Neuropteris and Ale- 

 thopteris, as w r ell as the known Megalopteris species, might well have 

 descended, that name may conveniently be employed in the hypothesis 

 to designate the type existing previous to the Middle Devonian, from 

 which the ncuropteroid, alethopteroid and tseniopteroid groups, includ- 

 ing in the latter some species of living marattiaceous genera, descended. 



1. See Dawson, Foss. PI. Dev., Upper Sil. Form. Can., Geol. Serv. Can., 1871. 



