THE MARYLAND CYCADS. 413 



possible exceptions the trunks appear to have been derived from more or 

 less arenaceous deposits, referable either to this or to the Patapsco forma- 

 tion. There is no very definite evidence that the Arundel, which is a 

 highly argillaceous terrane, has yielded any, unless, possibly, by secondary 

 deposition from the Patuxent formation. Most of the vegetable tissues 

 embedded in the Arundel are either carbonized or replaced by iron, silicifica- 

 tion at times occurring near its contacts with the more arenaceous Patux- 

 ent and Patapsco terranes or well to the landward, where its deposits tend 

 to be somewhat arenaceous within the formation itself. Near the Patapsco 

 contact, for example, a coniferous trunk partly lignitized and partly 

 silicified was found, and a silicified coniferous trunk was excavated from 

 an Arundel sand lens near Brookland. The circumstance that lignitized 

 cycad trunks have never been reported by the Arundel iron miners should 

 not, however, carry inuch weight, since if occurring they would doubtless 

 be compressed or otherwise distorted and therefore much less readily 

 recognized. Besides, unless the trunks occurred more commonly than in 

 the Patuxent and Patapsco formations, the chances of their being encoun- 

 tered at all b}^ the iron miners would be very slight, for no one has ever been 

 known to exhume a silicified cycad trunk from the perhaps equally numer- 

 ous Patapsco and Patuxent excavations for sands and gravel. One must 

 not infer, therefore, that the cycadaceous element of the vegetation of 

 Arundel times was necessaril_y less prominent than that of the Patuxent 

 and Patapsco epochs. The fact that there was such an element in the 

 Arundel flora is shown by the occurrence of frond impressions in its clays 

 and iron ores. The conditions for the entombing of the trunks may at 

 that time have been less favorable, as the conditions of permanent preser- 

 vation in such a form as to favor detection certainly were. 



There is no very definite evidence that any of the trunks have been 

 derived from, the Raritan terrane, though several may well have been. 

 The most probable case is that of the trunk, W. C, B., No. 6346, found 

 north of Woodwardville, but the point at which that trunk was found is 

 not positively known. Moreover, its much worn condition suggests 

 redeposition in the Pleistocene. 



That the original beds of the trynks were certainly largely arenaceous 

 instead of argillaceous is proved by their silicification, hereinafter men- 

 tioned, though semisilicified coniferous wood is occasionally found in 

 slightly sandy clays. 



