1892] MARYLAND ACADEMY OF SCIENCES. 197 



a Fauna and Flora of more modern type than that of the 

 Potomac occupied the country, and of course gave a dif- 

 ferent aspect to its features. The Fauna is represented by 

 the remains of crustacean shells resembling those of Cyclas, 

 of worm-bores similar to those of Scolithus, and of shells 

 apparently related to Unio. In the Flora, gymnosperms 

 and angiosperms abounded, but these were different from 

 those of the Potomac, and serve to distinguish the region 

 and its deposits.* 



These plant remains have not yet been studied closely 

 enough to establish their precise identity, but we may 

 readily recognize genera closely related to Cornus, Ficus^ 

 Laurus^ Myrioa, Sassafras and Phyllites, besides others 

 less easily recognizable. 



The excavations for tunnels and sewers and buildings 

 in and around the City of Baltimore within the last 25 

 years have brought to light the rocks which underlie this 

 region, and supplied much knowledge with regard to their 

 order of superposition, composition and later modifications. 



Prominent among these facts is that Avhicli shows this 

 city is underlaid at moderate depths, west of Central 

 avenue, by a nearly continuous bed of steatite and horn- 

 blendic gneiss, which is interrupted in the vicinity of 

 Union Depot by an upthrust of diorite. Indeed, in a few 

 places, snch as the deep cut on the south end of the Bolton 

 lot, the greenish steatite rock is overlaid by a belt of horn- 

 blendic gneiss of the foliated pattern. Farther south in 

 the same tunnel the hornblendic gneiss, and, where this is 

 absent, the steatite rock is overlaid by a bed of quartz 

 schist, of the pattern which formerly rested at the surface 

 in many places near Jones' falls and across the country 



*Tn my former paper, Proc. Amcr. Philos. Soc. 1888, p. 52, I referred to this for- 

 mation^certain marine remains of Encrinites, corals and braehiopods taken out 

 of pieces of white sandstone. These should be eliminated from the description, as 

 they were collected from rocks which ajipear to have been transported from the 

 North mountain. 



