452 GENERA INCERTAE SEDIS [CH. 



seed-bearing leaves of Ginkgo. We have as yet but little to guide 

 us in our attempts to trace the ancestry of that remarkable survival 

 Ginkgo biloba, and it is highly probable that, if more satisfactory 

 records of older members of the Ginkgoales were available, we 

 should be able considerably to extend the range in morphological 

 characters which in the present representative of the group is 

 comparatively restricted. The numerous leaf-bearing axes, many 

 of them branched, referred by Fontaine 1 to his genus Nageiopsis, 

 should not be overlooked from the point of view of their possible 

 relationship to Podozamites. The branching habit of these Potomac 

 specimens is no bar to an affinity to Podozamites if examples of 

 the genus are no longer to be interpreted in terms of a Cycadean 

 frond. Berry 2 , in a recent revision of Fontaine's genus, refers 

 some species to Podozamites which he still regards as Cycadean. 

 It is interesting to find on a specimen of Nageiopsis figured by 

 Fontaine a zone of crowded scars 3 (fig. 816, s) such as may be seen 

 on an Agathis shoot. 



Many of the leaves described as Podozamites are of little value 

 as evidence of the occurrence of the genus. In the case of imperf ec t 

 specimens of detached leaves it is often impossible to distinguish 

 between Podozamites, Phoenicopsis, and the leaves of Araucarian 

 plants, or pinnae of some species of Zamites. It is therefore net 

 possible to state with confidence the geological range of the genus. 

 Undoubted examples of Podozamites are essentially Rhaetic and 

 Jurassic fossils, and there can be no doubt as to the abundance 

 and wide geographical range of the genus in both these periods. 

 Such leaves as those recently figured by Hollick 4 from Cretaceous 

 beds of Long Island as Podozamites lanceolatus certainly agree 

 closely in form with that species, but they are all detached speci- 

 mens : the fragmentary leaves from the Middle Cretaceous beds of 

 the Amboy clays described as P. angustifolius (Eich.) and P. mar- 

 ginatus Heer 5 afford no proof of the presence of Podozamites: 

 similarly Velenovsky's species P. miocenica from Bohemia 6 might 

 equally well be referred to the genus Dammarites. Well pre- 

 served specimens have been described by Zeiller 7 from the 



1 Fontaine (89) B. p. 195. 2 Berry (10). 



3 Fontaine (89) B. PL LXXVI. fig. 5. 4 Hollick (12) Pis. 162, 163. 



5 Newberry and Hollick (95) PL xm. figs. 16. 



6 Velenovsky (81) PL i. figs. 1820. v ' Zeiller (03) B. 



