KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 51. N:o (0. 13 
Already in 1880 NATHORST (p. 66) suggests that Ptilozamites triangularis NATH. 
(NATHORST 1879, p. 62) and Piilozamites linearis NATH. (NATHORST 1879, p. 63) are 
identical with Pt. Heeri, and at the same time points out the possibility of Ptilo- 
zamites acuminatus NATH. (NATHORST 1879, p. 62) and Ptilozamites acutangulus NATH. 
(NATHORST 1879, p. 63) also being so. Later on he (1886, p. 122) separates Putilo- 
zamites triangularis as a forma latior and Ptilozamites linearis as a forma angustior, 
and places the fragmentary ”Ptilozamites acuminatus? pl. 12, fig. 5, NATHORST 
1879, under Pt. Heeri. Here he (1886, p. 123) also unites Ptilozamites acuminatus 
and Ptilozamites acutangulus, and points out the possibility of this species only con- 
stituting a variety of Pt. Heeri. Finally, he has made some unimportant alterations 
in the explanations of the plates (1886). 
Of the specimens originally described as Ptilozamites acuminatus and Ptiloza- 
mites acutangulus, there thus remain only -pl. 12, fig. 4 and pl. 18, fig. 2, NATHORST 
1879. They do not, it is true, agree in every way with the typical specimens of 
Pt. Heeri, their pinnae having an obliquely triangular shape, short and broad at the 
base; but on the other hand there is no reason to look upon them as separate 
species, both because they are too fragmentary to be regarded as such, and 
because transitional types are not missing. 
As already mentioned, NATHORST (1886, p. 122) instituted a forma latior and 
a forma angustior. I have withdrawn these, among other things because the fronds as 
regards size form a complete series. Whether the small specimens are to be regarded 
as young ones or not, can be decided here as little as in the case of Ptilozamites 
Nilsson; and the same possibilities of explanation are available. I have already 
stated the size of a frond to be 53 x 2-1 cm., but, presuming the same proportion 
between length and breadth, this seems to have been considerably exceeded, as there 
is one fragment which measures 2-8 cm. in breadth. 
NATHORST (1879, p. 60) drew attention to the fact that the pinnae of opposite 
sides are of a different length. Later finds show the same peculiarity (pl. 2, fig. 2; 
pl. 3, figs. 3, 12), so it seems to be characteristic of the species. It is therefore 
not quite inconceivable that the stalk was forked. Generally, fronds also have seg- 
ments below the point of bifurcation, but, as is well known, there are examples to 
the contrary. It may, however, be more likely that the specimens constitute entire 
fronds and that the asymmetry is due to the position of the fronds in relation to 
each other. If, for instance, they were placed in a very dense spiral, so that each 
frond partially covered or shaded the next one, the result might have been that they 
acquired this shape. 
Pt. Heeri constitutes a type of frond which is remarkable from several points 
of view. The enormous length and the narrow shape are striking, and give it a 
characteristic aspect. Fragments often show a considerable resemblance to Anomo- 
zamites; but Pt. Heeri is on the whole well delimited against species of other genera. 
Within the genus it is very closely related to Ptilozamites Carlssoni NATH. As for 
the differences between the two species, see Ptilozamites Carlssoni (p. 14). Pit. Heeri 
