ART. 22 TERTIARY FOSSIL PLANTS FROM ARGENTINA BERRY 9 



Genus PTERIS Linnaeus 



PTERIS NIRIHUAOENSIS. new species 

 Plate 1, Figures 3. 4 



Based upon small fragments of pinnae, habit of frond conse- 

 quently unknown. Pinnae linear-lanceolate, divided nearly to the 

 rachis into relatively long linear, ultimately pointed segments. The 

 sinuses are usually nearly symmetrically rounded and narrower than 

 the segments, but in some instances in maximum-sized fragments 

 the proximal lower margin of the segment is decurrent for a con- 

 siderable distance, subtending a space wider than the width of the 

 segments. The rachis is stout, prominent, and somewhat flexuous. 

 Margins entire, but faintly undulate. Texture subcoriaceous. Mid- 

 veins of the segments diverge from the rachis alternately at wide 

 angles and continue to the tips of the segments. They give off at 

 acute angles numerous laterals, the distal of which are simple sub- 

 tended by once forked laterals and these in turn by twice forked 

 laterals. This typical venation is not constant, however, for in 

 a great many instances there are cross connections resulting in a 

 reticulate venation, as shown in the accompanying figure. 



The largest fragment seen is that shown in Figure 3 and is of 

 a sterile pinnule. All of the specimens are much broken and dis- 

 torted, but what I have considered to represent a piece of a fertile 

 pinna is shown in Figure 4. This is slightly smaller than the sterile, 

 but agrees with it in form and venation. What I take to represent 

 a marginal indusium with its contained sori is a thick crust of car- 

 bonaceous matter along the margins of the segments. I could not 

 develop any spores or structural features in this thickened mass, and 

 it may simply represent revolute margins. However, its appear- 

 ance is significantly like fertile fragments of Pterls^ and I have given 

 this feature considerable weight in the identification of the fossils. 



The vegetative habit, as incompletely determinable from the 

 present fossils, is shared among a large number of fern genera, 

 among which I might mention Phegopte)^, Goniopteris^ Di^yopt&i'-is, 

 Cyathea, and ^GJeichenia as genera likely to occur in the Patagonian 

 Tertiary. All of these differ in having inframarginal sori and the 

 venation is not reticulate in Dryopteris (restricted), Cyathea or 

 Gleichenia (used in a supergeneric sense). Phegoptens sometimes 

 shows a similar reticulate venation, but it is more regular, as it is 

 also in those species of Gomopteru which are reticulate. 



Many species of Pterh have the form of the fossil, and a similarly 

 reticulate venation occurs in widely scattered forms in Asia and New 

 9o864r— 28 2 



