Bd. III: 14) 
THE MESOZOIC FLORA. 
69 
' Ptilophyllum (Williamsonia.>) pectinoides (PiiILL.). 
PI. 7, figs. 25 — 27. 
Cycadites peciinoides, Phillips 1S29. p. 125: pi, 10, fig. 4. 
PtilophvJlum pectinatiim, Morris, pars, 1841, p. 117. 
> Pterpphylliim rigidum, Andræ 1855, p. 42; pi. ii, fig. 1. 
Palœpzamia hasiula Bean niscr., Lf.ckenry 1864, p. 77. 
Williamsonia hasiula, CaRRUTHERS 1870, p. 693. 
PierpphvUum pectinoideum, Phillips 1S75, p. 226; pi. 10, fig. 4. 
IVillianisonia pecteu, Sew.vrd, pars, 1900 a, p. 20. 
Williamsonia pccten, Seward, pars. 1900, p. igo. 
In accordance with the older English writers, e. g. Phillips, I regard the two 
species described by him under the names of Cycadites pecteu and C. pectinoides as 
distinct. The former species occurs mostly in the Middle Estuarine Series in York- 
shire, the latter in the Lower Estuarine. Cycadites pecteu appears to have become in 
the course of time the better known through its abundant occurrence at the famous 
localities of Gristhorpe and Cloughton Wyke, whereas the latter species has been 
more or less neglected. Seward joins both forms into one species, choosing for it 
the better known name of pecteu and placing it in the genus Williamsonia. It is 
possible that all fronds of this type have belonged to Williamsonia; but this has 
not been proven, and isolated fronds are no doubt for the present better ranged 
within one of the form-genera on which the artificial classification of fronds is based. 
In distinguishing between P. pectinoides and P. pecteu as different species I am in 
accord not only with the older rvriters but also with Prof. Nathorst (1911, p. 19).^ 
The specimens referred to this species are shown in pi. 7, figs. 25 — 27. The 
more typical specimens are those in figs. 25 and 27; the one shown in fig. 26 is a 
little different. Of the former two specimens, the one in fig. 25 is an impression of 
the upper, the one in fig. 27 of the lower side of the frond. As far as can be made 
out, the fronds have been linear in shape. The pinnae are fairly dense, their bases 
in touch but not overlapping. It is very difficult to ascertain the exact mode of in- 
sertion; but it is clear that the pinnae are attached to the upper side of the rachis 
and somewhat obliquely. Both edges of the pinna appear to bend downwards in 
joining the rachis, the distal corner being somewhat rounded and the proximal de- 
current. The pinnae are linear in shape and taper gradually from the base; the apex 
is acute. The venation is not clearly shown; but on the impression of the lower 
side (fig. 27) there are seen some fine, subparallel, somewhat spreading veins. 
' I am not able to decide whether the Stonesfield plant figured by v. Sternberg (1823, pL 33, fig. i) 
as Polypodiolites peciiniformis. later known as Palœozamia pectinaia (Brgn.) and recently included by Seward 
(1904) in Williamsonia peclen should be regarded as identical with Ptilophyllum pectinoides. Should this 
be so, the latter name, being younger, must be rejected, and the species named P. peciiniforme (Sternu.). 
