328 Systematic Paleontology 



solid ; vascular bundles of the petioles arranged in a row entirely around 

 them and near the margin of a cross-section, also sometimes a few near 

 the centre ; spadices abundant, irregularly scattered over all parts of 

 the surface, usually showing the marks left by the essential floral organs 

 or a central cavity occupying their place, surrounded by curved or 

 crescent-shaped pits concentrically arranged in several rows and set 

 concave to the axis of the spadix, representing the involucral bracts; 

 armor varying from 25 mm. to 75 mm. in thickness, this variation often 

 great in different parts of the same specimen ; cambium layer indistinct ; 

 liber zone not generally distinguishable from the wood ; the latter in two 

 or three zones, medullary rays faint; medulla well marked, homogeneous, 

 usually spongy in appearance. 



This species represents a type quite distinct from all the others, the 

 cycadean trunks of Maryland being divisible, according to habit, into two 

 classes, one of which would embrace all the forms included in the six 

 species above described, and the other those that have been referred to 

 this species. The fact that the rock in the latter is always firm, hard, 

 and heavy, and usually dark colored, is not merely an accident of preser- 

 vation, but results in some obscure way from the nature of the vegetable 

 tissues. The trunks are generally larger and the leaf scars much larger, 

 though they have nearly the same form and arrangement. The repro- 

 ductive organs are more abundant and usually very regular and definite 

 in their character. 



This species, with Oycadeoidea Fontaineana, is scarcely less numerous 

 than Cycadeoidea marylandica, these three being by far the most abun- 

 dant of the Maryland trunks. 



Cycadeoidea Clarkiana Ward 

 Plate XLIX 



Cycadeoidea Clarkiana Ward, 1906, Mon. U. S. Geol. Surv., vol. xlviii, 1905, 

 p. 472, pi. Ixxxix, figs. 1, 2, 4; pi. cvi. 



Description. — Trunks rather large, tall and subcylindrical or barrel- 

 shaped, laterally compressed, unbranched; rock rather hard, of a light- 

 ash color and average specific gravity; organs of the armor horizontal 



