SPHENOPTERIS. 109 



would have been retained had there not been a Carboniferous fern 

 of the same name. 



In looking at the specimen (V. 2242), PI. VI. Fig. 2, and at that 

 figured in PI. VII. Fig. 1 (V. 2327), or the one with still more 

 deeply lobed pinnules (V. 23270), Fig. 10, p. Ill, we seem to have 

 two distinct species represented by these extreme forms. A careful 

 examination of the several specimens included under the present 

 species clearly demonstrates a gradual transition from one form to 

 another, and I am unable to draw any satisfactory line between the 

 various forms of fronds. The resemblance of certain specimens to 

 species already described from other localities and horizons is pointed 

 out in the descriptions of the individual fragments. Some of the 

 specimens I was at first disposed to place under Sphenopteris 

 Pichleri, Schenk, 1 as more perfect examples of that fern than 

 appear to have been available when the species was instituted. 

 It is extremely difficult to decide in certain cases whether the 

 better course is to separate specimens by distinct names when they 

 differ in the details of form shown by the ultimate segments, or to 

 include them under one name. Neither plan will lead to final and 

 satisfactory results so long as we have only fragments of sterile fronds 

 and pinnae to guide us. On the whole the inclusion of these frond 

 specimens in S. Fittoni appears to me the preferable course, which 

 may or may not be justified by the acquisition of more perfect 

 material. In speaking of S. Pichleri, Schenk draws attention to 

 the Hymenophyllaceous appearance of the pinnules; this same filmy 

 character is well seen in some of the English forms of S. Fittoni, 

 especially in the case of V. 23270, shown in Fig. 10, p. 111. The 

 chief differences between the specimens of S. Fittoni, which have 

 some resemblance to S. Pichleri, Schenk, also S. Cordai, Dunk., 2 

 and the type specimen figured by Fitton, consist in the more 

 divided pinnules and the more filmy nature of the lamina ; the 

 latter character is, however, not very trustworthy, as it may be only 

 apparent and really due to differences in the rock matrix, thus 

 being simply an accident of preservation rather than an original 

 character. 



In addition to the species referred to below as resembling in 

 a greater or less degree S. Fittoni, there may be mentioned 



1 Palaeontographica, vol. xxiii. p. 166, pi. xxix. figs. 2-5. 



2 Ibid. vol. xix. p. 210. 



