1888] MARYLAND ACADEMY OF SCIENCES. 23 



sand, about six feet thick, holding an abundance of the Miocene 

 shells, Perna maxillata and Ostrea percrassa. Farther down the 

 Patuxent river no other exposures of the upper Eocene marl 

 appear to view, but on the western banks of the stream, above 

 Cole's Creek, the Miocene blue sandy clay takes its place and 

 emerges from below the tide level. From Nottingham to below 

 Naylor's Landing the shores are low, and the Eocene dark marl 

 rises only a very few feet above the water ; but upon going- 

 back into the country, the densest of all the Eocene quartzites 

 comes to view above the marl, and forms a stratum three or 

 four feet thick, enclosing numerous common fossil shells and 

 their casts. 



At a distance of somewhat more than a mile below Pope's 

 Creek, near the base of the cliifs adjoining the Potomac river, 

 another kind of coarse hard quartzite projects in a broken layer 

 of a foot or less in thickness. This variety of rock is also 

 fossiliferous, and contains a small proportion of quartz pebbles, 

 but the only fossils observed therein were small and too obscure 

 to be accurately determined. This rock, however, forms a part 

 of the undoubted Eocene marl bed, which continues up the 

 river and affords the Cardita planicosta, Pectunoulus stamineics, 

 and other characteristic fossils of this formation. 



Leaving this region and extending our observations to the 

 neighborhood of Crownsville and along the Annapolis and Elk- 

 ridge railroad, we find the Eocene fossils mixed through the 

 masses of siliceous limestone scattered over the surface or buried 

 deep in the ferruginous sands and sandy green marl. Here 

 countless numbers of casts, and occasionally shells, of Cardita 

 planicosta, Oytherea ovata, Crassatella alta, Domiiopsis meekii, 

 Turritella mortoni, and small specimens of Ostrea compressirostra, 

 may be met with over many acres of ground. Here, and 

 extending more particularly towards the southwest, the hills 

 are abrupt, somewhat conical, and superficially composed of 

 ferruginous sand, while beneath them and in every deep ravine 

 the dark greensand or more sandy upper marl makes its appear- 

 ance. Proceeding down the railroad towards Annapolis, almost 

 every deep cut and sandy hill, when not obscured by Quater- 

 nary sand or sandstone, yields Eocene fossils, either on the 



