20tl: Sellards — Validity of Idiophyllum rotundifoliicm. 



species common at the locality. The outline and cordate base of 

 the pinnules, and especially the faint indication of lobation of 

 the upper border, just above the base (figure 2), are characters 

 of iV''. rarinervis. Although the lateral nervation is mostly 

 obscured, there can be little doubt regarding the specific iden- 

 tity. The lateral venation shown in figure 2 is taken from 

 several pinnules. The lateral pinnae are somewhat more 

 crowded than is usual for iV\ rarinervis^ a condition explained 

 by the immaturity of the frond. The plant is a difficult object 

 to photograph, but the figure here given will perhaps help to 

 clear up some of the peculiarities attributed to the fossil. The 

 appearance of nerves " sometimes crossing each other in con- 

 trary directions and forming by intervention regular quadrate 

 or rhomboidal meshes •' is caused by the crowding and overlap- 

 ping of the pinnules. 



Figure 2. — A single pimiule ; showing the characters of Neuropteris rari- 

 nervis Bnnb. ; taken from the right side of the specimen, x 2. 



Altogether, it seems evident that the species Idiophyllum 

 7'otundifoliicm is a synonym of J^euroj^teins rarinervis, and 

 that the genus Idiophyllum has no status in systematic fossil 

 botany. 



Through the courtesy of Mr. David White, the writer has 

 recently had an opportunity of examining the type of Idio- 

 phyllum rotundifoliicm^ now in the Lacoe Collection of the 

 United States ]^ational Museum. The plant is not entirely 

 freed from the matrix, the tips of the lateral pinnae on the 

 right side and at the top being still partly covered. Mr. 

 White had also recognized that the fossil represents an imma- 

 ture frond, and agrees with the writer that it is Neuropteris 

 rarinervis. 



Yale University Museum, Geological Department. 



