LANCE FLORA OF EASTERN WYOMING 133 



There are 27 specimens clearly referable to this well-defined species, from two locaUties in 

 the Lance Creek area. Most of the speciraens are well preserved, although the venation seems 

 always to be only faintly impressed, as a result of the thick texture of the leaves. 



Pistia corrugata was described by Lesquereux from abundant remains in the upper Mesaverde 

 group at Point of Rocks, Wyoming. The original description is as follows: 



"Leaves broadly obovate, incrassated from the middle toward the base, bordered upward 

 by a wavy margin, gradually narrowed into a short pedicel with bundles of radicles at its base; 

 veins going out from the pedicel in two or three compact fascicles, dividing in passing up from the 

 base of the leaves, and forming, by cross-branchlets, large irregular polygonal meshes." 



The abundant specimens in the Lance Creek coUections do not differ in any respect frora the 

 above description. Coraparisons with 'the type speciraens at the U. S. National Museura have 

 shown that the average size of the Lance Creek leaves is soraewhat greater than that of the type 

 specimens figured by Lesquereux. Berry has raade the same observation on specimens from the 

 Whitemud formation of Saskatchewan. There are, however, several unfigured specimens from 

 the Mesaverde formation in the collections at the U. S. National Museum which closely approach 

 in size the Lance and Whitemud specimens. On the basis of other variatious observed in a large 

 number of specimens frora the Fox Hills and Colgate, Brown has synonyraized the speciraen of 

 Ottelia americana Lesquereux and one speciraen of Lemna scutata Dawson with Pistia corrugata. 



As known at present, the leaves of P. corrugata, which are usually well defined and fairly 

 common, are valuable index forras for the Montana and post-Montana Cretaceous. They are 

 now known from the Mesaverde, Judith River, Kirtland, Belly River, Whiteraud, Fox Hills, 

 Colgate, and true Lance formations. No comparable leaves have ever been reported from the 

 extensive "Fort Union" flora of the Rocky Mountain region. The Wilcox species, Pistia wil- 

 coxensis, is regarded by Berry as " clearly distinct from previously described fossil forms of Pistia." ' 



The reference of these fossil leaves to the genus Pistia has been amply substantiated by 

 comparison with leaves of the single living species. They are, indeed, difficult to separate from 

 the leaves of the modern "water lettuce," Pistia stratiotes Linne,- which is widespread in south- 

 eastern United States, Mexico, and Central and South America, and is known also in Asia and 

 Africa. 



Occurrence— Localities P3853, P3858. 



Collection—l!. C. Mus. Pal., Plesiotypes Nos. 2488, 2489, 2490; No. 2491. 



Family CANNACEiE 



Genus CANNA Linn^ ? 



Canna? magnifolia Knowlton 



(PlateS, Fig. 1) 



Canna'! magnifolia Knowlton, U. S. Geol. Surv. Prof. Paper 101, 2.54, pl. 30, fig. 3, 1917. Berry, U. S. Geol. 

 Surv. Prof. Paper 185-F, 129, 1934. Dorf, Bull. Geol. Soe. Amer., vol. 51, 222, 225, 1940. 



The specimen here figured is the better of 2 incomplete leaves of this type in the Lance 

 Creek collections. Except for the somewhat larger angle of divergence of the secondary venation, 

 these leaves cannot be distinguished from the figured and type specimen of Cannal magnifolia 

 from the Verraejo forraation of Colorado. The Medicine Bow specimen referred to Canna cf. 

 C? magnifolia differs only in the ab.sence of the alternation of thick and thin veins.' I have not 

 been able to compare these specimens with the reported example of this species which Berry de- 

 scribed from the lower Lance (Hell Creek) formation of South Dakota.'' 



The uncertainty regarding the taxonoraic affinities of this species has been discussed in my 

 cited report on the Medicine Bow flora. 



Occurrence — Localities P3652, P3853. 



Collection—\5 . C. Mus. Pal., Plesiotype No. 2492. 



' Berry, E. W., U. S. Geol. Surv. Prof. Paper 91, 175, pl. 113, fig. 4, 1910. 

 » New York Botanical Garden, aheets Noa. 18, 2687. 



> Dorf, E., Carnegie Inst. Waah. Pub. No. 508, pt. I, 49, pl. 2, fig. 5, 1938. 

 * Property of Mr. Henry Lee, of Rapid City, South Dalfota. 



