86 RUFFORDIA. 
pteris acrodentata, Font., suggested a reference of the English 
forms to this Potomac species, but, on carefully looking through 
the large series of specimens in the National Collections, it is 
impossible to come to a satisfactory conclusion as to where the line 
of demarcation should be drawn expressive of specific differences. 
There is undoubtedly a very marked difference between Pl. VI. 
Fig. 1 and the specimen represented in Pl. IV., but this is rather a 
divergence suggestive of two varieties than one to be regarded as 
of specific value. If we had only these two extreme forms to deal 
with, there would be no hesitation in speaking of them as distinct 
species, but, as already pointed out, we have a large number of 
intermediate forms which, in my opinion, bridge over the apparent 
gap between the ends of the series. 
The chief differences between such specimens as Pl. VI. Fig. 1 
and the forms of Ruffordia Gépperti previously described, consist 
in the greater breadth of the ultimate segments and the more open 
character of the pinne. The venation of the pinnules is very 
distinctly shown in the figured specimen, Pl. VI. Fig. 1a; the veins 
are flabellately disposed and repeatedly forked; the margin of the 
pinnules are, for the most part, distinctly dentate. Cf Fontaine’s 
figure of S. acrodentata, pl. xxxiv. figs. 4 and 4a; also Mantell’s 
figure of S. Phillipswi.’ 
On the same piece of ironstone, associated with the sterile 
portions of a frond, occur fragments of small fertile fronds ; also 
several pieces of fronds with the rachis tripinnately branched and 
showing very little leaf lamina, the serrate divisions of the ultimate 
branches recalling, to some extent, Onychiopsis Mantelli (Brong.). 
Possibly these different fragments belong to the same plant, but of 
this there is no real evidence. Ecclesbourne. Rufford Coll. 
V. 2355. The rachis and venation of the pinnules distinctly 
shown. Very similar to V. 2333, but the segments somewhat 
narrower. Ecclesbourne. Rufford Coll. 
V. 2158, V. 2827, V. 2357, V. 2357a. These specimens are 
regarded as fragments of the same variety. Ecclesbourne. 
Rufford Coll. 
1 Potomac Flora, p. 90, pl. xxxiv. fig. 4. 
2 Geol. 8.E. England, p. 239, fig. 2. 
