66 CONTRIBUTIONS TO PAL.EONTOLOGY 



nensis, which Sanborn, at about the same date,' considered more appropriately referred to the 

 genus Aralia. It seems to me that the species might equally well be a Viburnum. In my private 

 herbarium I have a number of leaves of the Asiatic Viburnum seiboldiif, whose characters, particu- 

 larly of venation and marginal teeth, appear to be more Hke those of the fossil specimens than are 

 those of any Aralia. In the range of size and shape variations, moreover, these Viburnuin leaves 

 can exactly match the variations seen in the leaves of Celastrus taurinensis and its synonynious 

 forms. In view of the scarcity of leaves of this type in the Medicine Bow collections, however, 

 it does not seem desirable to make further changes in the taxonoray, but rather await the revision 

 of the Fort Union flora by Dr. Roland W. Brown, who has a large suite of specimens of this species 

 at his disposal at the U. S. National Museura. 



This species is evidently widespread and of long geologic range in North America. In 

 addition to its recorded occurrences, there are also several perfect specimens of it in the unclassified 

 material from Black Buttes, Wyoming, which I have consulted at the U. S. National Museum. 

 It is one of the few Medicine Bow species which ranges up into the Fort Union of the Rocky 

 Mountain region. As seen in the citations above, it is also common in the Eocene of the Gulf 

 Coast and of Oregon. Any attempt to separate the late Cretaceous forras from those of the 

 Paleocene and Eocene on justifiable grounds has been futile, although the Cretaceous specimens do 

 seem to be more lanceolate in average shape. Whether or not this character can become the basis 

 for specific separation remains to be seen in subsequent studies. 



Occurrence — Corson Ranch, Wyoming, Locs. P. 371, P. 372; north of Walcott, Wyoming, 

 Loc. P. 373; Elk Mountain road, Wyoming, Loc. P. 374. 



Collection—\5 . C. Mus. Pal., Plesiotypes Nos. 1350, 1351, 1352. 



Family RHAMNACE^ 



Genus RHAMNUS Lmn6 



Rhamnus salicifolius Lesquereux 



(Plate 12, Figs. 4, 5; Plate 13, Fig. 4) 



Rhamnus salicifoliiis Lesquereux, Am. Jour. Sci., 2d ser., vol. 45, 206, 1868; U. S. Geol. and Geog. Surv. Terr., 



Ann. Rept. (1869), 196 (reprint, 1873); Rept. U. S. Geol. Surv. Terr., vol. 7, 282, pl. 53, figs. 9, 10, 1878; 



Ivnowlton, U. S. Geol. Surv. Prof. Paper 101, 271, 1917; idem, Prof. Paper 130, 154, pl. 15, fig. 4, pl. 19, 



fig. 2b, 1922. 

 Rhamnus salicifolius Lesquereux?. Ivnowlton, U. S. Geol. Surv. Bull. 163, 70, 1900; idem, Prof. Paper 155, 



107, pl. 46, fig. 12, 1930. 

 Rhamnus bebrwntensis Knowlton and Cockerell, U. S. Geol. Surv. Bull. 696, 544, 1919; ICnowlton, U. S. Geol. 



Surv. Prof. Paper 130, 155, 1922. 

 Rhamnus elegans Newberry, New York Lyc. Nat. Hist. Annals, vol. 9, 49, 1868; U. S. Geol. Surv. Mon. 35, 



117, pl.'50, fig. 2, 1898. 

 Juglans larandensis Knowlton, U. S. Geol. Surv. Prof. Paper 130, 120, pl. 20, fig. 12, 1922. 

 Ficus? smiihaoniana? (Lesquereux) Lesquereux. Knowlton, ibid., 130, pl. 21, fig. 4. 



Lanceolate leaves, referable to Rhamnus salicifolius, are abundant and widespread in the 

 Medicine Bow formation. More than 20 well-preserved specimens in the collections indicate 

 considerable variation in size, yet are identical in secondary and tertiary venation and general 

 shape. The average characteristics are precisely as shown in Lesquereux's original figures,^ 

 except that the reconstruction of the broken tip of his figure 9 should apparently have been con- 

 siderably elongated. In view of the intergrading variations observed in the Medicine Bow speci- 

 mens, it is evident that the species listed above as synonymous are merely shght variants of the 

 average leaf forra of Rhamnus salicifolius. It seems desirable to re-describe this species on the 

 basis of the abundant material collected. 



Description (Supplementary) — Leaves typically narrowly lanceolate, narrowing gradually 

 from below the middle to an elongate acute tip, and raore abruptly below to an equilateral or 

 shghtly inequilateral cuneate base; length 5 to 12 cm., width 1.5 to 2.5 cm., average dimensions 

 apparently about 10 by 2 cm., petiole short, thin, up to 1 cm. long; midrib firm, relatively straight; 

 10 to 14 pairs of thin, mainly alternate secondaries leaving the midrib at angles of 25° to 45°, curv- 

 ing uniformly upward toward the margins, converging, unbranched, paralleling margins and 



> Sanborn, Ethel I.. Carnegie Inst. Wash. Pub. No. 465, 27, 1935. 

 'Lesquereux, Leo, Rept. U. S. Geol. Surv. Terr., vol. 7, pl. 53, figa. 9, 10, 1878. 



