﻿DISCOVERIES AND COLLECTIONS. II 



to the cycad collection of the United States National Museum. The specimen is 

 well silicified and bears various young fruits. The horizon from which it was 

 eroded out is supposed to be either the Lower Chico or the Horsetown beds of the 

 Lower Cretaceous, and hence a little more recent than or else of much the same age 

 as the upper of the two Black Hills cycad horizons.* 



OCCURRENCE AND DISTRIBUTION OF NORTH AMERICAN FOSSIL CYCADS IN TIME. 



With the addition of the twenty species included in the new genus Cycadella 

 of Ward, the assigned number of North American silicified cycadeoidean trunk spe- 

 cies now numbers sixty. These are given in the following list, arranged according 

 to geological horizons : 



(i) Upper Jurassic, Wealdeu, or Lower Cretaceous of the Black Hills of South 

 Dakota and Wyoming: Cycadeoidea aspera, cicatricula, Colei, colossalis, 

 dacotensis, excelsa,formosa,furcata, heliochorea, ingens, insolita,Jenneyana, 

 McBridei, Marshiana, minnekahtensis, nana, occidentalism Paynei, protect, 

 pulcherrima, reticulata, rhombica, Stillwelli, super ba, turrit a, IVellsii, 

 II 'ielandi, 



(2) Upper Jurassic of central Wyoming and the Black Hills (about 150 feet below 



No. 1 preceding, in heavy shales of the Atlautosaurus beds of Marsh, or 

 Morrison Formation, as used in recent reports of the United States Geo- 

 logical Survey): Cycadella Beecheriana, carbonensis, cirrata, compressa, 

 concinna, contracta, crcpidaria, exogena, ferruginea, jejuna, jurassica, 

 gelida, gravis, Knightii, Knowltoniana, nodosa, ramentosa, Reedii, utopi- 

 e/isis, verrucosa, wyomingensis (all Ward's species). All except C. utopi- 

 eusis are from the Freezeout Hills, Carbon County, Wyoming. 



(3) Potomac Formation of Maryland (iron ore beds between Baltimore and 



Washington) : Cycadeoidea marylandica (Fontaine), Tysoniana, Fontaine- 

 ana, McGeeana, Uhleri, Bibbinsi, and Goucheriana (last six species Ward). 



(4) Jurassic of Colorado (near Boulder): Cycadeoidea nigra Ward. 



(5) Pre-Laramie (?), near Golden, Colorado : Cycadeoidea {Zamiostr obits) mirabilis 



(Lesquereux). 



(6) Dakota formation (?), southern Kansas : Cycadeoidea munita Cragin. 



(7) Upper Trias, North Carolina; locality unknown: Cycadeoidea Emmonsi 



(Fontaine). 



(8) Trias of Prince Edward Island : Cycadeoidea abequidensis Dawson. 



(9) Trias of York, Pennsylvania : Cycadeomyelon yorkense Fontaine. 



(10) Trunk from Lower Chico or Horsetown beds (=Dakota Cretaceous or older), 

 Grapevine Valley, Colusa County, California. 



* See Monogr. U. S. Geol. Surv. , vol. xlviii, p. 276. 



