330 ROYAL SOCIETY OF CANADA 
are Cretaceous, although they range as far down as the Potomac form- 
ation. From this it is apparent that while specific forms may be 
definitely associated with particular horizons, the general facies of the 
genus as a whole is such as to indicate an Upper Cretaceous or even 
Tertiary contact, rather than a Lower Cretaceous. 
Populus cyclophylla, Heer, and Sassafras cretaceum, Newb. (46: 
p. 98), are both well defined elements of the Dakota flora, and they 
thereby give a somewhat definite indication of a specific horizon, which 
is certainly Upper Cretaceous. Again, both Quercus flexuosa, Newb., 
and Q. coriacea, Newb., are known so far only in the Puget Sound 
Group of Chuckanutz, Washington (46: pp. 73, 74), once more giving 
a definitely Upper Cretaceous horizon. Similarly also, Cycadites un- 
jiga, Dn., from the Upper Cretaceous of the Peace river, compared by 
Dawson (9: p. 20) with C. dicksoni, Heer, from the Upper Cretaceous 
of Greenland, confirms the deductions to be drawn from the foregoing 
facts in a very striking manner, especially as Dawson has already shown 
the Peace river formation to be Senonian, and thus within the limits 
of the Chico. Cladophlebis is a very strongly pronounced Cretaceous 
type, which is largely found in the Potomac formation, though it is 
also common to the Upper Cretaceous of Vancouver Island, from which 
Iccality Dawson has described C. columbiana (12: iv, 55), a type, how- 
ever, which is quite distinct from those generally associated with the 
Cretaceous, and which affords no direct point of comparison with the. 
present species. ; 
Nilsonia pasaytensis stands by itself as a species, but reference to 
the general distribution of the genus shows that although it may be 
recognized in the Upper Cretaceous, as recorded by Dawson (9: iv, 24), 
its range is rather through the Lower Mesozoic. Thus, Ward (57: 
p. 90 et seq.) enumerates four Cretaceous species, of which one is from 
the Kootanie and three from the Shasta series, and six species of Juras- 
sic age, a distribution in exact accord with the limits assigned by Zeiller 
(59: p. 238), who speaks of its tolerable abundance in the Rhætic, 
whence it passes through the Jurassic to the Lower Cretaceous. The 
general evidence of distribution, therefore, is toward greater abundance 
in the Middle Mesozoic rather than toward its close, and in this sense 
the present species would afford very strong evidence of a Lower Cre- 
taceous horizon. Furthermore, in comparing this species with those 
previously described by Fontaine and others, there is seen to be a 
somewhat remarkable correspondence with N. nipponensis, Yokoyama, 
as figured by Ward (57: pl. xvii, f. 8-10), which tends to strengthen 
the idea that this.is at least an early Cretaceous type. 
