OF THE GENERA ZAMITES AND PTEROPHYLLUM. 193 
The question as to the genus, to which the frond described here should be referred, 
is a difficult one, and the following genera may now be considered in this 
connection. 
Sphenozamites.—1t does not appear to me to be possible to attribute the Raibl fossil 
to this genus, as at present defined. The name Sphenozamites was proposed by 
Brongniart, in 1849, to include fronds of the Ofozamites-type, which were not auriculate 
at the base, and possessed a radiating nervation. In the specimens referred to Spheno- 
zamites and figured by Zigno *, Renault f, Seward 1, and others, the spreading nature of 
the nervation is clearly seen, and the shape of the pinnules more closely approximates to 
the rhomboidal than to the cuneate form. The margin in some species is also toothed. 
It might, perhaps, be possible to extend the diagnosis of this genus so as to include 
the Raibl species, but at the present time such an attempt would hardly seem advisable. 
Zumites—The specimen discussed here appears to be quite distinct from the fossils 
attributed to this frond-genus, both as regards the shape of the pinn:e, and in respect to 
the nervation. As compared with Zamites grandis, the nerves are sometimes finer and 
closer, and there is no evidence of a callosity at the base of the leaflet. Zeiller§ has, 
however, recently described a frond from the Rheetic of Tonkin under the name Zamites 
truncatus, Zeiller, in which the shape and nervation of the leaflets offer some points 
of comparison with the present specimen, but the pinnæ are much smaller, and the 
agreement is not a close one. 
Pterophyllum.—It is admitted that this plant differs from typical members of this 
genus in a marked degree, especially as regards the size and shape of the pinnæ. Yet 
it appears to me to be more closely allied to Pterophyllum than to any other frond 
genus with which I am acquainted. In some of the typical species of Pterophyllum 
from the Triassic rocks, especially P. longifolium, Brongn.|, the leaflets are sometimes 
contracted at the base and broadest at the apex, thus approximating in some slight 
degree towards the cuneate form, though they are on a much smaller scale than iu 
P. Bronni. If we were to imagine such a frond magnified several times and the 
wedge-like shape of the pinne further accentuated, we should arrive at a leaf which 
would correspond fairly closely with the latter species both in form and nervation, 
On the whole we may conclude that the Raibl fossil agrees with the diagnoses of this 
genus given by Brongniart, Zeiller, and others, with the chief exception that the pinne 
are broadly wedge-shaped in form and not linear. It would thus seem preferable to 
adopt Schenk’s provisional reference of this plant to the genus Pterophyllum, than to 
make use of Schimper’s term Macropterygium. 
It remains to be pointed out that detached pinnæ of this frond, especially when 
fragmentary, are liable to be mistaken for the leaves of Cordaites and other genera 
m which the nervation is closely similar, but which are simple leaves, spirally arranged 
* Zigno (1873), vol. ii. p. 105, pls. 39 & 40. 
t Renault (1893), p. 327, pl. 81. fig. 1. 
+ Seward ( 1904), p. 119, pl. 11. fig. 4, and text-‘ig. 12 on p. 120. 
$ Zeiller (1902), p. 166, pl. 43. figs, 3-6. || Cf. Leuthardt (1903), pt. i. p. 16, pls. 7-10. 
