248 THE FLORA OF THE DAKOTA GROUP. 



It seems as if the genus had, from its first appearance, gradually lost its 

 power of differentiation to take up, by its leaves, the unalteral)le cliaracters 

 under wliich it is known and described from the different stages of tlie Ter- 

 tiary as L. Proraccinii. A few unim2)ortant deviations from that specific form 

 have been described under different names, but they are now generally rec- 

 ognized by authors as mere varieties. Under the name of L. Procacchiii 

 Ung., linger and Massalongo have' described leaves from the Tertiary of 

 Ttalv; Heer from the Miocene' of Greenland, and Saporta and Marion from 

 the Pliocene of Meximieux. These last authors, however, reproduce the 

 figure of the leaf in Heer's Fl. Foss. Arct., vol. 1, PI. xxvii, Fig. 5, with the 

 name of L. iskindicum, considering it as typical of the living L. tidipiferii 

 Linn., Avhile the leaves described in the flora of Meximieux are supposed 

 to represent an extinct type. But the deviations from the normal form of 

 the Tertiary leaves are miimportant; therefore L. Jiclvcficioii Fisher-Ooster, 

 figured by Heer, Fl. Tert. Helv., PI. cviii, Fig. 6, and probably also the 

 fragment described as L. Hamri Ett, Foss. Fl. v. Bilin, pt. 3, p. D, PI. xli, 

 Fig. 10, of Avhich, however, the essential parts of the leaf, its outlines, are 

 undiscernible and are also mere varieties of L. Procaccinii Ung. The char- 

 acters of this species, derived from L. gif/anfeum of the Dakota Group, are 

 mostly reproduced in the North American L. tuJipifpiyt Linn., the only living 

 species of oiu* epoch. 



The Dakota Group has numerous leaves wdiich, by their characters, 

 have such a degree of affinity to those of Menispermum and Cocculus, two 

 genera still represented in the North American flora, each by one abun- 

 dantlv distril)uted sjjecies, that it is not possible to object to their reference 

 to this family of plants. The leaves of Menisperndfes arerifoViHS Lesq. 

 (Cret. Fl., PI. XX, Figs. 1-4), compared to those of Cocculus carolinus DC, 

 and of Menispermum canadense Linn.; those of Meiiispermites gmndis, M. 

 n/clopJi/jUus, etc. (Cret and Tert. Fl., pp. 79 and 80, PI. v. Figs. 1-3), com- 

 jiared also to some of the leaves of 3Ienispermum cmmdensc, and h\ their 

 peltate mode of attachment of the petiole to those of Stephania or of Cissam- 

 pdos pareira of Mexico, show that relation in full evidence. 



In a fossil state, nine species of Menispermites are represented by leaves 

 in the Dakota Group, two in the schists of Atane and one in the Peace and 

 Pine River series of Canada. None have as yet been found in the U))i)er 

 Cretaceous and from more recent formations one species only. Cocadus 

 Ilaydenianus is descril)ed by Prof War<l and figured in splendid leaves from 



