BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 



Vol. 26. pp. 335-342 AUGUST 17, 1915 



PROCEEDINGS OF THE PALEONTOLOGICAL SOCIETY 



PALEOBOTANIC EVIDENCE OF THE AGE OF THE MORRISON 



FORMATION ' 



BY I'DW.VIJD WILBER BERRY^ 

 (Read before the Paleniifolor/iral Sociefi/ Deceuiher -U). V-HJf) 



CONTENTS 



Page 



I iitroductory 335 



Age of the I'otomac group 336 



Age of the Wealden 338 



Age of the Kootenai 338 



Summary 341 



Introductory 



1'lie only fossil plants that have been recorded from the Mon-ison for- 

 mation are the silicified fragments of cycad stumps which occur in such 

 abundance in the Freezeout Hills of Carbon County and at one or two 

 other localities in Wyoming. These were described by Ward- and re- 

 ferred to the genus Cycadella. About a score of so-called species which 

 were based on external appearance were described. Neither the genus 

 {('jjcadellu) nor aJiy of the species have ever been found outside the 

 Morrison formation, so that they furnish no direct evidence regarding the 

 age of the deposits. They are, however, very close to the similarly silici- 

 lieil trunks of Cijcadeoidea in their habit and general plan of organization. 

 The Cycadeoidea remains are common in the Lakota formation oL' the 

 Black Hills rim and in the Patuxent formation of Maryland. In the 

 absence of studies of the internal structure of the Morrison genus Cyca- 

 della. it is not certain that it can ))(> nuiintainod as distinct from Ci/rn- 



' Contribution to the symposium held at the Philadelphia meeting December 30, 1914. 



Manuscript received by the Secretary of the Society April 3, 1015. 

 -Li. W. Ward: Description of a new genus and twenty new species of fossil cycadean 

 Ininks from the Jurassic of Wyoming. I'roc. Wash. Acad. Sci., vol. i, 1000, pp. 2r.:{-300. 

 .Iiir!issi<: cycads from Wyoming. Mon. U. S. Geol. Survey, vol. xlviii. lOOO, pp. 170- 

 203, Ills, xlvi-lxlil. 



