1890] 



MARYLAND ACADEMY OF SCIENCES. 99 



dull quartz sand and small pebbles, having the general appear- 

 ance of broken, crude alum. One of these beds directly under- 

 lies the first exposed cliff of the Black Marl below the Round 

 Bay boat-house. A minute detailed account of this member 

 must be deferred to a future occasion, since it alone would 

 furnish materials for an extensive memoir. It, however, forms 

 a stratigraphic unit of great distinctness, and occupies the 

 same relative position as that which is held by the Laminated 

 Sands in New Jersey. 



Above and extending seaward from the clay-sands rises the 

 great Loicei- Marl Bed, which here is marked by three distinct 

 units of composition. The lowest is the Blach Mad, which 

 forms a body of clayey sand, often indurated at base, and some- 

 times loaded with large masses of dense iron-stone. It is fully 

 50 feet thick in its greatest development, has suffered erosion at 

 various points along its exposed surfaces next the river and 

 creeks, and along its inward thin extension it is densely 

 charged with leaves and fragments of plants and trees. At 

 frequent intervals and at various levels it is also loaded with 

 the iron-coated, friable casts of many species of fossil shells, 

 typical of the Cretaceous, and it holds besides two or three kinds 

 of shark's teeth. 



On top of the Black Marl, and sometimes settled into it so 

 as to show no base line of demarcation, appears the Clay Marl. 

 This differs from the preceding by being usually of a more or 

 less greenish color, composed of fine sand, loaded with clay of 

 a pinkish drab or lead-color, but which when altered by atmos- 

 pheric agencies appears yellow or pale brown. It forms a con- 

 nected series of beds, or an irregular stratum, at most 30 feet 

 thick, but usually not more than about 12 to 20 feet thick. 



Next above this Clay Marl rests the thick deposit of fine 

 sands which, for the sake of present recognition, we have 

 called the Mottled Sands. This is a very conspicuous member 

 of the series, which grades below into the sand of the Clay 

 Marl, and from which there is often no appreciable line of 

 demarcation. The sands composing it are not so fine as in the 

 member next above. They are generally of a pale greenish 

 color, streaked and spotted with orange or paler yellow patches, 

 or short stratified aggregations, discolored by ferrugination. 



