LANCE FLORA OF EASTERN WYOMING 129 



Shaparenko,' who has studied the past records of Ginkgo in detail, does not regard G. laramiensis 

 as a vahd species. Brown, on the other hand, distinguishes between G. adiantoides and G. lara- 

 miensis on the basis of the character of mature average leaf forms.^ He states: "During Upper 

 Cretaceous time the average form was still cuneate, but the tendency was to be entire, undulate, 

 or only slightly bilobate, as in G. laramiensis. From the Eocene onward the average type was 

 reniform and bilobate and is typified by G. adianloides." This is certainly a valid observation, 

 but is impossible to apply, as Brown has pointed out, unless abundant specimens are secured. 

 In the Lance Creek collections, only a single, incomplete specimen is known, so that a positive 

 specific reference cannot be made. 



As is indicated in the long list of references above, the well-defined leaves of this form are of 

 common occurrence in the Upper Cretaceous and Tertiary rocks of North America. Whether 

 or not a single species of Ginkgo has survived from the Upper Cretaceous to the present day cannot 

 be determined on the basis of leavcs alone. 



Occurrence — Locality P3857. 



Colledion—U. C. Mus. Pal., No. 2460. 



Family TAXODIACE.E 



Genus SEQUOIA Endlicher 



Sequoia dakotensis Brown 



(Plate 6, Figs. 4-11) 



Sequoia dakoknsis Brown, Jour. Washington Acad. Sci., vol. 25, 447, 1935; U. S. Geol. Surv. Prof. Paper 1S9, 



247, pl. 48, figs. 6-10, 1939. Dorf, Bull. Geol. Soc. Amer., vol. 51, 218, 222, 225, 1940. 

 ISequoia nordenskioldi Heer. Knowlton, Proc. Washington Acad. Sci., vol. 11, 207, 1909. 



There are 20 specimens of cone impressions and casts in the collections. The excellent 

 preservation of one of these (plate 6, fig. 7) as a mud cast makes it possible to compare it with the 

 casts described by Brown as Sequoia dakotensis. The description given by Brown is as follows: 



"Cones, L5-4 cm. long, 1.2-3 cm. in diameter, with about 30 scales, arranged in two sets 

 of spiral rows, the steep-angled set in 5 rows, and the flat-angled set in 3 rows. The faces of the 

 scales present sections that are long and narrow, roughly diamond-shaped, but occasionally with 

 one or two additional angle.s. Peduncles of the scales abruptly narrowed to the point of attach- 

 ment at the axis of the cone. Surface of the scales smooth, or sometimes slightly wrinkled." 



The single cast in the Lance Creek collection has 28 scales; an examination of the large 

 number of typical specimens of this species at the U. S. National Museum has shown that this 

 number of scales is within the range of variability of "about 30 scales," as described above. The 

 remaining characters of the cone and of other cone impressions in my collections are precisely as 

 enumerated by Brown. 



At the Lance Creek localities which have yielded them, these cones are always associated 

 with foliage which is clearly of the Seqiioia type (plate 6, figs. 4-6). In view of this invariable 

 association and the absence of other coniferous foliage at these localities, it is reasonably certain 

 that the cones and foliage belong to the same species. This foliage cannot be distinguished from 

 that of such nominal "species" as S. langsdorfii (Brongniart) Heer, S. nordenskioldi Heer, or S. 

 obovata Knowlton.' These "species" have little meaning, either botanically or geologically, 

 because of their lack of distinguishing characteristics. On foliage characters alone they cannot be 

 separated from the living S. sempervirens Endlicher. When foliage remains are intimately asso- 

 ciated with well-defined cones, however, there can be no natural or valid grounds for referring 

 the foliage and the cones to two distinct "species." 



OccMrre^ce— Localities P3651, P3652, P3855, P3857, P3859. 



Collection—V. C. Mus. Pal., Plesiotype.s Nos. 2461, 2462, 2462a (counterpart), 2463, 2464, 

 2465, 2466, 2467, 2468; Nos. 2469, 2470, 2471, 2472, 2473. 



' Shaparenko, K., Philippine Jour. Sei., vol. 57, pt. 1, 1-28. 1935. 

 ' Brown, R. W., U. S. Geol. Surv. Prof. Paper 189, 247, 1939. 



' For the numerous references to these wideapread forms, consult Knowlton, F. H., U. S. Geol. Surv. BuU. 696, 594, 

 595, 596, 1919. 



