254 UNITED STATES GEOLOGICAL SURVEY— TERTIARY FLORA. 



I have recognized a variation of tlic surface, the upper one being more 

 generally smoolli than the lower, which also shows the veins somewhat thicker. 

 Even the tissue of the leaves is often hardened by muddy deposits under the 

 floating leaves, and thinner in those raised above water by longer pedicels. 

 These fossil leaves, however, all present the upper surfiice, as can be seen by 

 the reflexed border of figs. 1 and 2; and the same difference in the characters 

 remarked above, as also iu tiie less number of. nerves of this species, are 

 observable upon all tlic fragments from Golden, and up(ni the two leaves, 

 of JV. tenuifolium, one of which only is represented here, and which were 

 obtained from a different locality. 



Hahitat. — Sand Creek, Colorado {P/of. A. Gardner). 



MALVOIDEiE. 

 BiJTTNERIACE^. 



DOMBEYOPSIS, Ung. (emend.). 



This genus, as indicated by the termination appended to its name, is still 

 unsettled, and the species referred to it are of uncertain attribution. It would 

 be therefore useless to expose its historical records on mere hypothetical con- 

 siderations. Five species of Domheyopsis are described from the Miocene of 

 Europe ; to some of them, the leaves of our pi. xlvii have a relation more or 

 less defined. Massalongo has briefly described twenty species of the same 

 genus, mostly from the Eocene of Mount Bolca. The photographs from the 

 specimens of three of tliem have been communicated to European paleo- 

 botanists, but I know the leaves merely from the descriptions. Schimper 

 remarks, in Pal. V^gdt., p. 607, "that evidently, of the numerous Do^nheyopsu 

 described by Massalongo, some are mere duplicates, or varieties; others are 

 rather referable to Aralia, or to analogous genera, than to this Domheyopsis, 

 a genus moreover merely provisionally established." Even Massalongo refers 

 some of them to Ampclophyltum, Grewia, etc. Saporta considers many of 

 them as representing species of Tilia. 



Dombcyo|>»<is platan oidcs, sp. nov. 



Plate XLVII, Fijis. 1, 2. 



LeaveB subcoriaceous, very entire, cordate, broadly ovate, snbtrilobate, obtuse, abruptly short- 

 pointed ; nervation tliree-i)aluiate; lateral veins equidistant, thick, the lower ones branching outside, 

 craspedodroiue with their divisions. 



These leaves, of large size, averaging nine centimeters both ways, have 



