74 CONTRIBUTIONS TO PAL^ONTOLOGY 



cuneate base; length 5 to 14 cm., width 5 to 11 cm., average dimensions appear to be about 9 by 8 

 cm.; petiole thick, long, up to 5 cm.; venation palmate, tri-nerved from the top of the petiole, 

 strong, tlie midrib straight or slightly zigzag toward the apex, craspedodrome with 4 or 5 

 pairs of strong, subopposite secondaries, straight, subparallel, diverging from the midrib at an 

 angle of 20° to 30°, more rarely up to 35° but never higher; two lower pairs of secondaries usually 

 branched once or twice, the branches passing to the marginal teeth; lateral primaries diverging 

 at the same angle as the secondaries on the midrib, often shghtly longer than secondaries, giving 

 slightly trilobate character to the leaf ; each lateral primary with 4 to 6 acute secondary branches 

 on its lower side, the lowest of which bears num.erous, usually camptodrome branches, while the 

 upper branches are unbroken, or often once or twice branched and craspedodrome; branches 

 occasionally also developed on upper side of lateral primaries near the margins, usually craspedo- 

 drome; tertiary venation strong, the nervilles both broken and percurrent; margin entire below 

 to near the middle of the leaf, becoming denticulate above, the teeth smali, usually acute, occa- 

 sionally slightly obtuse; texture firm. 



Lesquereux originally included in Vihurnum inarginatum, several smaller leaves of quite 

 different character,' which both Knowlton and Berry later agreed should be separated into a new 

 species. The evidence from the Medicine Bow collections substantiates separation, since the 

 smaller specimens of V . marginatum (see plate 15, figure 3) are consistently of the same character 

 as the larger specimens. It is, of course, possible that this species may have had two entirely 

 different leaf forms among the smaller leaves. Whether or not this is probable must remain a 

 matter of opinion until branches bearing both kinds of smaller leaves be discovered. 



From the same locality from which V. marginatum was described Lesquereux obtained 

 several larger specimens of what he called V. platanoides. These he distinguished from V. mar- 

 ginatum by the "less numerous, more open, lateral veins, whose branches are more curved in 

 passing up to the borders, and especially by the enlarged truncate or subtruncate base of the 

 leaves." ^ I was at first inclined to regard the leaves of this type as large forms of V. marginatum, 

 but failed to find a single form among the hundreds of Medicine Bow specimens which possessed 

 the essential characters of V . platanoides. Moreover, the large specimens in the collections main- 

 tained consi.stentIy the diagnostic characters of V. marginatum. It seems evident, therefore, that 

 these two species are distinct, as Isjiowlton has previously concluded.' 



The abundant material of V. marginatum now available makes it possible to revise the status 

 of several late Cretaceous specimens referred to various species of Platanus. The specimens which 

 Ward obtained from the type locality of Viburnum marginatim and which he referred to the 

 Dakota species Platanus heerii are clearly referable to the former species in every respect. The 

 Raton and Laramie specimens referred to P. platanoides by Knowlton are easily distinguished 

 from that species by their cuneate bases, shape, and venation. I am also convinced that the 

 Raton specimens referred to P. guillelmw heerii and the Denver specimen referred to P. aceroides 

 laiifolia are indistinguisliable from the larger specimens of Viburnum marginatum, which are often 

 shghtly trilobate in shape. 



The previous and present record of V. marginatum indicates that it is an extremely wide- 

 spread, abundant, and easily rccognizable species, which is limited stratigraphically to deposits of 

 latest Cretaceous age. It is unknown from the extensive floras of indisputable Paleocene or later 

 age of the Rocky Mountain region. It may possibly be present in the Paleocene of Texas.'' The 

 exact formation here is in doubt, however, and the specimens (= Platanus aceroides latifolia) 

 have not been figured, making the occurrence of doubtful value. 



The generic status of Viburnum marginatmn has suffered considerable vacillation between 

 the genera Viburnum and Platanus. Lesquereux originally referred the species to Viburnum on 

 the basis of comparison with the modern V . pubescens Pursh, V. dentatum Linn6, and V. lantanoides 

 Michx. Heer subsequently discovered leaves which he considered conspecific with V. niarginatum 

 in the Tertiary (Eoccne?) of Unartok, Greenland, and referred the species to Platamis. Heer's 

 specimens are undeniably platanoid and are closely associated with typical platanoid fruits, but 

 the leaves are clearly different in shape and basal characters from Lesquereux's specimens, and, 

 as Holhck has pointed out, "should be regarded not only as specifically but also as generically 



' Lesquereux, Leo, Rept. U. S. Geol. Surv. Terr., vol. 7, pl. 37, fig. 11, pl. 38, figs. 2, 3, 5, 1878. 

 ^Lesquereux, Leo, U. S. Geol. and Geog. Surv. Terr., Ann. Rept. (1874), 314, 1876. 

 ' Knowlton, F. H., U. S. Geol. Surv. Prof. Paper 130. 146, 1922. 

 * Berry, E. W., U. S. Geol. Surv. Prof. Paper 91, 13, 1916. 



