TODITES. 



91 



differences in the form of the pinnules which render the inclusion 

 of Schenk's species in the list of synonyms inadvisable ; the two 

 forms, however, are closely allied. 



Amongst the numerous specimens of ferns of the Cladophlebis 

 type figured by Heer from the Jurassic and Cretaceous rocks of 

 Siberia and other northern regions, we find several fronds, or rather 

 fragments of fronds, which are probably closely allied to or even 

 identical with Todites Williamsoni. He applies the generic name 

 Asplenium 1 to many of the leaves without adducing satisfactory 

 evidence of the relationship to the recent genus. The fertile frag- 

 ment of Asplenium whitbiense figured by this author appears to 

 agree in the distribution of the sporangia and in the shape of the 

 segments with the present species, and differs from the specimens 

 in which the sori bear a resemblance to those of Asplenium. Wliile 

 feeling confidence in the identity of some of Heer's so-oalird 

 Asplenium species from Siberia with Todites Williamsoni, it is 

 practically hopeless to attempt an accurate determination of the 

 species without a careful examination of the fossils themselves. 



In Fontaine's Potomac Flora, which we now know to include 

 both Wealden and Jurassic species, there are several examples of 

 Cladophlebis fronds which may be reasonably identified with 

 Todites Williamsoni. Fontaine's zeal for the institution of new 

 species led him to adopt new names for plants which in some cases 

 he admits bear a striking resemblance to known European forms ; 

 he has frequently described under distinct specific names portions 

 of fronds which one would reasonably expect to find as parts of 

 one large leaf. Cladophlebis virginiensis, Font., is in all probability 

 identical with Todites ; it agrees very closely with the English 

 specimens with the larger pinnules, but in the absence of fertile 

 pinna3 it is almost impossible to speak with certainty. The 

 examples with smaller pinnules which he names Cladophlebis pare a 

 agree exactly with the smaller forms of Todites Williamsoni, as 

 represented in PL XXI. Fig. 6 of this Catalogue; similarly, his 

 C. distans is probably identical with the same species. Fontaine 

 refers to the similarity of his Cladophlebis parva and Pecopteris 

 dentata of Lindley & Hutton, and adds, " one may well hesitate 

 to separate them"; but he considers the venation is not quite 



1 Heer (77), ii. pi. xxi. fig. 4. 



