1889] MARYLAND ACADEMY OF SCIENCES. 57 



mortoni. This same character of marl keeps on up towards 

 the head of the ravine as far as the stream, and its lateral 

 branches have cut deeply into the body of the ridge. Here, as 

 in all the rest of this section of country, the overlying loamy 

 marl is covered up towards the surface with the Quaternary 

 ferruginous sand, more or less gravelly, or with a pale yellowish 

 sandy clay of somewhat uniform texture. 



On the opposite side of the stream, but beginning at a much 

 lower level, perhaps half a mile nearer the entrance, rounded 

 and much broken hills appear, carved out of the bordering 

 highland. These hills are moderately steep, sloping at an 

 angle of from about 50° to 60°, and are separated at irregular 

 intervals by eroded gullies. They rise at first forty to fifty feet 

 above the stream, and farther back are merged into the body of 

 the ridge. Rains and other atmospheric agencies have been 

 cutting into the surface of these elevations, so that the outlying 

 members have been greatly reduced in height, the sides have 

 been sloped oflF, and the more abrupt projections have been 

 overthrown and precipitated into the flood-bed of the stream. 

 Rapid waters have poured against the sides of the gullies, 

 enlarged their openings, washed the loose debris down to lower 

 levels, and coming in contact with fallen marl, sand, fossils, 

 and earthy mixtures, have made a wide, deep lining along the 

 margin of the stream, extending into its bayed-out openings on 

 the right bank. This section of the ravine is chiefly made up 

 of a mixture of fossil shells, greensand marl, quartz-sand, and 

 loamy clay thrown together in a confused manner, and com- 

 posing the greater part of hills which rise sixty feet or more 

 above the level of the stream. 



As the base of these exposures is always hidden by fallen 

 debris, sometimes to a thicloiess of ten feet, it is not always 

 possible to examine the materials of which they are composed. 

 But beginning at a level of about fifty feet above the river, 

 these fossiliferous mixed beds come into view, while the black 

 beds of the opposite side rise out of the bottom of the branch at 

 a little higher level. In these mixed beds the fossils are densely 

 aggregated into more or less silicified masses or layers, and they 

 aiford a much larger number of species than the black marls 

 which occur farther back in the ridge. dec. is, -sq. 



