6 ERNST ANTEVS, THE SWEDISH SPECIES OF PTILOZAMITES NATH. 
As has been mentioned, Ptilozamites is distinguished from Ctenopteris only by 
its segmentation; but as classification based on a difference in this respect is scarcely 
appropriate, it is principally on account of other circumstances that I retain the 
name of Ptilozamites. 
NATHORST (1897, p. 25) once suggested that Ptilozamites and Ctenozamites 
(= COtenopteris) ought to be regarded as palaeobotanical subgenera under one and the 
same botanical genus, but such a classification can hardly, I think, be suitable. 
The principal reason for keeping Ptilozamites, according to my opinion, lies in 
the intermediate position which this genus holds between Ctenopteris and Anomo- 
zamites. Agreeing with the former in all except the segmentation, it bears a con- 
siderable resemblance to the latter in all respects, and it is impossible to point to 
any distinguishing character which satisfactorily separates it from either the one or 
from the other. The possibility of uniting all the three genera cannot, however, be 
taken into consideration, and it is therefore probably best to keep Ptilozamites as a 
connecting link between the two other genera. 
Anomozamites is among other things characterized by parallel veins. Ptilozamites 
also has forms with parallel veins; but in this genus the veins are, as a rule, more 
or less radiating and more frequently forked. Regarding the shape of the pinnae 
the genera seem to be rather analogous. 
The consistence of the two genera seems to have been somewhat different. At 
least, Anomozamites minor (BRNGN.), which I have examined, has a considerably 
thinner cuticle than any Ptilozamites. The stomata are of an appearance common among 
the Cycadophytes, exactly as in the recent Zamia L. and Encephalartos LEHM. and 
in the fossil Otozamites pterophylloides BRNGN. and Dictyozamites Johnstrupi NATH. 
(both from Bornholm) among those I have had the opportunity of examining. 
In his ”Fossil Plants SEWwWARD (1910, p. 5346) compares Ptilozamites with Thinn- 
feldia ETT., and says that there ”can be little doubt as to the very close alliance 
between the Rhaetic species referred to these two genera”. Those forms of Thinn- 
feldia which were separated from this genus and classed as Dicroidium GOoTH. and 
the dichotomical species of Ptilozamites, no doubt, present certain analogies, but they 
can, I think, hardly be regarded as being closely related. 
Though it is difficult to point out any general, quite typical character, the 
Swedish species of Ptilozamites agree considerably on the whole. At the same time 
they are, as a rule, well delimited against each other. Two of them, viz., Ptilo- 
zamites Nilssomi NaArH. (pl. 1, figs. 1—3; pl. 2, fig. 8; pl.”3, fig. 5) and Pt. fallax 
NaATH. (pl. 1, fig. 8; pl. 2; fig. 6) are bifurcated, and this character combined with 
others gives them a typical appearance. Two other species, Pt. Heeri NATH. (pl. 2, 
fig. 2; pl. 3, figs. 1—3, 12) and Pit. Carlssomi NarH. (pl. 2, figs. 4, 5) are of a pe- 
culiar linear shape, and, finally, Pt. Blasii (BRAUNS) NaArtH. (pl. 1, figs. 9, 10; pl. 2, 
fig. 1; pl. 3, fig. 10) is distinguished by the size of the frond and the pinnae. 
Regarding the position which Ptilozamites takes in the system, I think it is 
impossible to express a decided opinion for the present. NATHORST placed it in the 
Cycadophytes, and this group was the first that came to hand, there being then 
