60 TRANSACTIONS OF THE [1889 



alaeformis, and specimens of Dosiniopsis meekii. It does not 

 form such a stony mass as that next above, nor is it as loose as 

 we find beneath the silicified beds nearer the Patuxent river. 



The entire exposure in this cliiF appears to be about sixty 

 feet thick, and its upper portion is continued in the loamy 

 greensand marl which keeps on up to within fifteen feet of the 

 coarse pebbly surface. The base of this cliif is deeply covered 

 by material from above, which has been continuously washed 

 out towards the channel of the Piscataway, adjoining which it 

 forms a terrace overlying the Albirupean clay. This part of 

 the formation lacks the basal black marl of the same period 

 which holds the Latiarca gigantea. But it runs back to near 

 the wide brook, about a quarter of a mile farther northeast, 

 where the same fossils occur as have been recorded from the 

 ravines near Old Farmington. 



Passing up the bed of this brook, which runs next the high 

 hill of Cretaceous black marl, on the eastern boundary of the 

 wide cove, and following its moderately straight course for a 

 distance of about one-third of a mile, the Eocene compact black 

 marl makes its appearance on both sides of the ravine. Its base 

 in the bed of the brook appears to be at a level of fully fifty 

 feet above the water of the Piscataway. The banks here are 

 abrupt cliffs, which are followed above by two or three stages 

 of erosion to the summit of the hill, and form steep slopes as 

 they ascend. Most of these acclivities are hidden by the depo- 

 sition of surface material washed from above, but the slippery 

 marl of the louver section forms an abrupt wall upon which 

 nothing can lodge. At the bottom, however, trickling water 

 keeps the border of the stream persistently wet, and makes a 

 bed of mire two or three feet in depth. Several of these black 

 marl banks present themselves in this vicinity, appearing most 

 of the way up to the source of this brook and upon its .lateral 

 branches. In the lowest of these exposures, the Latiarca gigantea 

 occurs from three or four feet above the bed of the stream up 

 to about eighteen feet. The Ostrea oompressirostra, Dosiniopsis 

 meekii, Orassatella protexta and Modiola sp? also appear sparingly 

 at or above this same horizon. Most of these shells, besides 

 Turritella mortoni, are bedded in colonies, and excepting the 



