Maryland Geological Survey 163 



the Potomac and several others are closely related to species which 

 occur in the Potomac. Six of these are forms which do not range 

 above the Patuxent-Arundel in the east. No characteristic Patapsco 

 species is known from the Kootanie, nor have any dicotyledons been dis- 

 covered. There are also represented several species which are not known 

 from horizons later than the Wealden and Neocomian, while both Daw- 

 son and Fontaine have recorded several Jurassic (Oolite) species in this 

 flora, although these particular identifications are not entirely above 

 suspicion, since neither of these students was always as careful as is desir- 

 able in some of their comparisons. Nevertheless several types which are 

 usually considered as especially characteristic of Jurassic floras, such as 

 Ginkgo and Protorhipis, are represented in the Kootanie flora. 



There are also present a large number of Kome species (Greenland) 

 and several from the Barremian of Europe, so that the Kootanie cannot 

 be considered younger than the Patuxent-Arundel of Maryland, and it 

 may be in part slightly older, although the two were at least partly 

 contemporaneous. 



The Kootanie flora is of especial interest because its relations with 

 the older Morrison formation make it possible to compare the Patuxent- 

 Arundel flora and the contemporaneous reptilian fauna with, the corre- 

 sponding flora and fauna of the Morrison-Kootanie. The age of the 

 Morrison (Atlantosaurus beds of Marsh, Como beds of Scott, Beulah 

 shales of Jenney, etc.) has long been disputed, vertebrate paleontologists, 

 who alone have been competent to speak on the subject, having, with the 

 exception of Williston regarded them as Jurassic. The latter author has 

 on several occasions pointed out their probable Lower Cretaceous age.^ 

 Lull's studies of the Arundel Reptilia lends considerable weight to 

 Williston's position. Fisher " has traced the Kootanie southward into the 

 Big Horn basin, where it was named the Cleverly formation by Darton, 

 and has differentiated the Morrison beneath the former in the Great 

 Falls area, where there is no apparent unconformity between the two. It 



^Williston, Journ. Geol., vol. xiii, 1905, pp. 342-350; vol. xviii, 1910, p. 93. 

 "Fisher, Economic Geol., vol. iii, 1908, p. 77; Bull. U. S. Geol. Surv., No. 356. 



