DICTYOPHYLLUM 139 
fragment of Clathropteris Minsteriana, Schenk, enlarged by Schenk 
from the lower portion of a large frond, the venation becomes very 
similar to the Dictyophyllum type. 
In Nathorst’s description of the genus! attention is drawn to 
the extreme variability of the species, and the consequent difficulty 
of determining specific and variety limits. 
Schenk, in Zittel’s ‘‘Handbuch der Paleontologie,’’*? includes 
Goppert’s genus Zhaumatopteris under the generic term Dictyo- 
phyllum. Bartholni,? in a recent contribution to the fossil flora 
of Bornholm, has referred certain specimens to /ausmannia, 
Dunk., which I am inclined to regard as Dictyophyllum fronds. 
This author considers that Dunker’s genus should be retained 
for certain forms of reticulately veined leaves; his figures of 
leaf fragments sufficiently demonstrate the great variation in 
the form of the lamina of such leaves. Bartholni’s figures of 
Hausmannia Forchhammeri, Barth.,£ agree closely with those of 
H. dichotoma as given by Dunker® and Schenk®; in the description 
of the Bornholm fossils no reference is made to this close resem- 
blance to Schenk’s North German specimens. So far as it is 
possible to base any definite opinion on such small specimens 
as those in the British Museum Collection, it is very probable 
that Hausmannia Forchhammeri, Barth., and Dietyophyllum 
Roemert, Schenk, may be the same plant. The nature of 
Dunker’s genus, Hausmannia,’ is far from clear; in the 
‘‘Wealdenbildung” the type specimen of this genus is figured, 
but unfortunately there is no detailed description or drawing 
of the venation. In habit the plant may be compared to Dic- 
tyophyllum acutilobum,® Schenk, from which it is distinguished 
by the longer and narrower segments. Schenk makes use of this 
doubtful genus for some small fragments found in the North 
German Wealden rocks,’ but his figures are by no means con- 
1 Foss. Fl. Schwedens, p. 13. 
Vol. io p. los. 
5 Bot. Tids. Bot. For. Kjévenhavn, vol. xviii. Heft i, 1892, p. 26. 
4 Loc. cit. pl. xi. figs. 4-6; pl. xii. figs. 1-3. 
5 Wealdenbildung, pl. v. fig. 1. 
6 Paleontographica, vol. xix. pl. xxix. figs. 8 and 9; pl. xxxi. fig. 3. 
7 Wealdenbildung, p. 12. 
8 Fl. foss. Grenz. Keup. Lias, pl. xx. 
9 Paleontographica, vol. xix. p. 223, pl. xxix. figs. 8 and 9. 
