Maryland Geological Survey 329 



or somewhat descending; rows of scars from left to right making an 

 angle with the axis of 45°, those from right to left an angle of 80°; 

 leaf scars subrhombic or irregular in shape and variable in size, 15 mm. 

 to 18 mm. wide, 10 mm. to 15 mm. high ; leaf bases present, sunk about 

 1 cm. below the surface, porous ; vascular bundles not visible on the 

 cross-sections, but distinct on the eroded surfaces; ramentum walls very 

 thin and sharp edged, thickening below to 3 mm. to 5 nun. hard, destitute 

 of markings or division line between the plates; reproductive organs 

 obscure and reduced to pitted areas on the eroded surface; armor 3 cm. 

 thick, the leaf bases passing insensibly into the woody axis ; wood 2 cm. 

 thick, in four layers or rings ; outer layer 1 cm. thick, chiefly composed 

 of the elements of vascular tissues passing upward and outward through 

 it and cundng over at the outer margin to enter the deflexed leaf bases ; 

 fibrous zone of three rings, the outer and inner consisting of loose, open 

 tissue, largely decayed in the only specimen that shows them, leaving a 

 fissure, the middle ring hard and firm, forming a plate surrounding the 

 medulla, 5 mm. thick, its inner surface regularly marked with the scars 

 of the medullary rays, which are elliptical in shape and disposed in 

 alternating rows; medulla very large and prominent, elliptical in cross- 

 section, thickest in the middle of the trunk to conform to its shape, which 

 it chiefly determines, the shorter diameter varying from 9 cm. to 15 cm. 

 and the longer from 14 cm. to 18 cm., coarse grained and homogeneous 

 in structure, its surface where exposed handsomely marked by the ridges 

 and flutings of the bases of the medullary rays rising out of it. 



This is a very distinct species and the only one of the Maryland Poto- 

 mac species that has the tall subcylindrical form. 



Cycadeoidea Fishery Ward 



Plate L 



Cycadeoidea Fisherce Ward, 1906, Mon. U. S. Geol. Surv., voL xlviii, 1905, 

 p. 470, pi. Ixxxvii, fig. iii, 9; pi. cv. 



Description. — Trunks rather small, about 30 cm. high and 20 cm. in 

 diameter, conical, unbranched; rock soft, light buff colored, of low 

 specific gravity; leaf stalks strongly inclined, making an angle with the 



