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C O N T R I B U T I O N S TO PAL^ONTOLOGY 



the presence of any one of the restricted Lancian species in an assemblage of un- 

 known age should indicate Lancian age. In actual practice, however, no such 

 assumption can be made with confidence, since an extension of the range of some of 

 these species can reasonably be expected to be made by future discoveries. An 

 association of a number of these restricted species in a fiora should indicate Lancian 

 age. Some species are considered more rehable than others because of their abun- 

 dance and their well-defined characters. Also there are a few species which are 

 absent from the type Lance, for unknown reasons, which are abundant in other 

 floras of Lancian age. The complete association of species which I consider the 

 best indices of Lancian age is as follows : 



Anona? robusta 

 Dombeyopsis trivialis 

 Ficus? eeratops 

 Fraxinus leii 

 Grewiopsis saportana 

 Laurophyllum vvardiana 

 Magnoiiophyllum cordatum 



Menispermites cockerelli 

 Nelumbo tenuifolia 

 Pistacia eriensis 

 Platanophyllum montanum 

 Sabalites eocenica 

 Viburnum marginatum 



In addition to these restricted species there are others which though of wider 

 stratigraphic range are, so far as is known, abundant only in floras of Lancian age. 

 These dominants are as follows : 



Cercidiphyllum eliipticum 

 Dillenites cleburni 

 Dryophyllum subfalcatum 

 Ficus planicostata 



Ficus? trinervis 

 Quercus? viburnifolia 

 Sequoia dalcotensis 

 Vitis stantoni 



Both of these lists are obviously to be regarded only as showuig tlie status of 

 these species in the present state of knowledge. As work progresses on the late 

 Cretaceous and early Tertiary fioras of the Rocky Mountain region there will un- 

 doubtedly be deletions and additions in both Usts. 



SUMMARY 



The present report discusses the fiora collected from the Lance formation at its 

 type locaUty, Niobrara C'ounty, Wyoming. The plant remains were obtained from 

 nine locaUties in the vicinity of Lance Creek; some additional specimens from this 

 area were secured through loan from the U. S. National Museiun. 



The type Lance formation Ues conformably above the Fox Hills sandstone, 

 which carries thc typical late Montanan marine fauna of the Splienodiscus zone, 

 and below the typical beds of the Paleocene Fort Union group. Numerous dinosaur 

 remains of the late Cretaceous Triceratops zone have long been known from the 

 same parts of the type Lance formation that have now yielded numerous plant 

 remains. Late Cretaceous mammals and fresh-water moUusks are also recorded 

 from the same beds. 



The flora of the type Lance formation, as described in the present report, com- 

 prises 70 recognizable forms, chiefiy of dicotyledons. There are 56 forms referred 

 to species previously known, 5 are described as new species, and 9 are given generic 



