Abstract

Introductory

The only fossil plants that have been recorded from the Morrison formation 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 Ward2 and referred to the genus Cycadella. About a score of so-called species which were based on external appearance were described. Neither the genus (Cycadella) nor any 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 silicified trunks of Cycadeoidea in their habit and general plan of organization. The Cycadeoidea remains are common in the Lakota formation of the Black Hills rim and in the Patuxent formation of Maryland. In the absence of studies of the internal structure of the Morrison genus . . .

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