CYCADOPHYTA 557 



which such specimens are known to the Portland 

 quarrymen. In certain trunks from the Sussex 

 Wealden, named Bucklandia by Mr. Carruthers, an 

 alternation of the scars of foliage and scale leaves 

 has been traced, such as is found in Cycas at the 

 present day. In some cases the stems attained a 

 more considerable height, as in the Cycadeoidea 

 gigantea of Seward, a fine specimen of which, almost 

 4 feet high, with a girth of i\ feet, was found some 

 years ago in the Isle of Portland, and is now set up 

 in the Geological Department of the British Museum. 1 

 In favourable cases the Cycad-like stems are completely 

 silicified, and their structure preserved with wonderful 

 perfection. A number of important specimens of 

 this nature, referred to many species, have been found 

 in our own country, France, Italy, and other parts of 

 Europe, but the United States of America are far 

 richer than any other country in such material. No 

 less than sixty species of silicified trunks of Cycado- 

 phyta have already been described from the Mesozoic 

 of North America, ranging in age from the Upper 

 Triassic to the Lower Cretaceous. In the Eastern 

 States the Potomac beds of Maryland (approximately 

 of Wealden age) have yielded seven species, but the 

 richest localities are in the West, on the Rim of the 

 Black Hills of Dakota and the Freezeout Hills of 

 Wyoming ; from the Upper Jurassic and Lower 

 Cretaceous beds of these districts forty -nine species 

 have been obtained. The specimens are very numerous ; 

 thus the twenty-nine species from the Black Hills of 



1 Seward, " On Cycadeoidea gigantea, a New Cycadean Stem from 

 the Purbeck Beds of Portland," Quarterly Journal of the Geol. Soc. vol. 

 liii. 1897. 



