140 CLADOPHLEBIS. 



from the Yorkshire Oolites. In Schenk's figure we have the apical 

 portion of a frond, which is characterized by the open habit of the 

 pinnae and by the rather short and broad form of the pointed 

 pinnules ; at the tip of the frond the pinnae are gradually replaced 

 by single falcate segments. The striking similarity leads me to 

 regard the German and English plants, although from different 

 geological horizons, as nearly allied, if not indeed identical. 

 Another specimen illustrated in Schenk's monograph, and named 

 Asplenites ottonis, 1 agrees in habit with A. Roesserti, but differs in 

 the appearance of the pinnules, which are fertile, and present 

 a corrugated surface due to the presence of sori parallel to the 

 secondary veins ; these are precisely the characters of the fertile 

 pinnae of C. denticulate (Pecopteris undans}. It may be suggested 

 that Asplenites ottonis is the fertile form of the frond referred by 

 Schenk to A. Roesserti', the very small fragment of the latter 

 species described by the same author as fertile is very imperfect 

 .and far from clear. While speaking of the fertile pinnules, 

 a comparison may be made also with some fragments figured by 

 Heer from Siberia, and referred by him to Asplenium whitliense ; 

 these possess long sori apparently with indusia disposed obliquely 

 to the midrib and parallel to the secondary veins, as in Pecopteris 

 undans. It is unfortunately impossible to make out the exact form 

 of the sori in the English specimens or to decide on the presence or 

 absence of an indusium, but so far as it is possible to judge, it 

 would appear that the sori may have been of a type similar to that 

 shown in Heer's figures, and to such as we find in some recent 

 Polypodiaceous species. 



In addition to the species Pteris frigida and P. longipennis 

 figured by Heer from Greenland, and included in the above list 

 as most probably specifically identical with Cladoplilelis denticulata, 

 there are some other fragments of fronds referred by the same 

 author to Pecopteris argutula, Aspidium Oerstedi, and other species, 

 which may be identical with C. denticulata ; but it is impossible 

 to decide as to the affinities of many of these fronds. It is not 

 improbable that the Australian fern named by McCoy 2 Pecopteris 

 australis, and compared by him with the English type, which 

 Bean named P. scarlurgensis, is identical with that species. 



1 Schenk (67), pi. xi. 



2 McCoy (74), p. 16, pi. xiv. fig. 3. 



