KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 5l|. N:O 3. 
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As typical forms may be regarded the specimens represented in pl. 3, figs. 1—9, 
of which the impressions shown in figs. 2 and 9 are counterparts of those in figs. I 
and 8, respectively, whereas fig. 7 is an enlargement of fig. 6. The fronds have 
rather thick rachises, which bear the pinnae on their upper surfaces. This can be 
inferred from the impressions of both the lower and the upper side of the frond. 
The impressions of the lower side show the bases of the pinnae abruptly cut off by 
the deep groove formed by the rachis. In those made by the upper side, the opposite 
pinnae can be seen to meet in the median line of the rachis. The manner of attach- 
ment of the pinnae is the one characteristic of Ptilophyllum. Both edges of the 
pinna bend downwards in joining the rachis: the distal edge thus becomes rounded 
and for some distance free from the rachis, the proximal one decurrent. The down- 
ward trend of the distal edge is seen on all the impressions of the upper side. The 
attachment of the proximal edges, on the other hand, is generally not shown, because 
of the ecrowded arrangement of the pinnae. These are very densely placed, imbricate, 
with the distal edge overlapping the proximal one at least in the lower portions of 
the pinnae. On impressions of the upper side, therefore, only the distal edges can 
be traced right down to the point of attachment, the proximal edges being prevented 
by the intervening portion of the next lower pinna from leaving any impression on 
the matrix. On impressions of the lower side, the attachment is naturally not shown. 
It is only in such exceptional cases, therefore, in which the pinnae are more remote 
from each other, that the attachment of the proximal edge can be clearly seen. A 
good example is shown in the enlarged photograph in pl. 3, fig. 7. In this case and 
in some others not quite so clear, the decurrence of the pinnae on the rachis is evident. 
In the specimens mentioned, the pinnae are of about the same type, narrow 
and linear, slightly falcate and pointed at the apex. The venation consists of spread- 
ing and occasionally bifurcating veins, 8—10 in number on an average. There is 
some difference between the specimens, however. In the fronds in figs. 6—9, the 
tapering of the pinnae towards the apex is rather rapid, the edges being parallel for 
quite a long distance. The specimens shown in figs. 1—4, of which those in figs. 1 
and 2 are counterparts of each other, are distinguished by more gradually tapered, 
more falcate, and sharper pointed pinnae. They show the same kind of attachment, 
however, and a similar venation. It is evident that the shape of the pinnae is sub- 
jected to a great variation in fronds of this type, and as there are also transitional 
forms, there seems to be no ground for separating the present specimens into different 
species. The little fragment shown in pl. 3, fig. 10, may quite well belong to the 
same species, too; the shortness of the pinnae is probably due to their place at the 
very base of the frond, since it is evident from other specimens — the one in pl. 3, 
fig. 1, for instance — that the pinnae rapidly diminish in length at the base. 
It is more doubtful whether the specimen in pl. 3, fig. 11, belongs to the same 
species. It is an impression of the lower side of a frond, with a portion of the thick 
rachis preserved in the matrix underneath the impressions of the pinna-bases, which 
are unusually well shown for an impression of the lower side. Although the actual 
point of insertion of the pinnae cannot of course be seen in a specimen of this kind, 
