1889] MARYLAND ACADEMY OF SCIENCES. 55 



On the same river, near Glymont, the dark micaceous com- 

 pact blackish marl forms the base and rises into the abrupt 

 cliff, overlaid by the greensand loam which becomes more 

 sandy and ferruginous above. This section aifords numerous 

 and fine specimens of Turritdla mortoni, with occasional single 

 valves of Ostrea compressh'ostra and well preserved Dosini- 

 opsis meehii and Crassatella capricranium. In this section the 

 shells are deposited in groups of a single species in a spot, a few 

 together in one place, as if the animals had been caught by the 

 overwhelming sand and buried at the place of their abode. But 

 few species have been obtained from this locality, but the spec- 

 imens are usually found in well preserved condition. 



As the black indurated marl is exposed farther east than this 

 region, no specimens of the large Latiarca gigantea have been 

 taken from the Glymont beds. Accordingly the Latiarca marl 

 must be looked for at a distance of about two miles back from 

 the Potomac river, where it occupies a diagonally directed ridge 

 extending from Tinker's Creek to the north shore of Matta- 

 woman Creek. No evidence of the presence of this large fossil 

 shell south of this side of the Mattawoman has yet been pro- 

 cured, but it abounds where it occurs. It is well known to the 

 people who reside in its vicinity, and they designate it in com- 

 mon speech as the " Turtle head." It seems to be confined to 

 that part of the lower Eocene marl which displays its greatest 

 thickness in a tract beginning about a mile east of the Potomac, 

 extending across a width of less than two miles back on the Pis- 

 cataway, and striking all the way down in a nearly southerly 

 direction, through the Mattawoman swamp, to the bend of that 

 creek, where it becomes narrow or has been mostly eroded away. 



West and northwest of this region, on Pomonkey Neck, we 

 search in vain for traces of the Eocene formation, or its under- 

 lying Cretaceous marls. But, a mile or more back from the 

 Potomac river, we enter deep ravines in the highlands, and 

 there once more the black Eocene marl, overlying the loamy 

 greensand of the Cretaceous, appears in large deposits, support- 

 ing the mixed and silicified shell-limestone which rises to the 

 summit of the less elevated hills. Here a wonderful spectacle 

 meets the observer, in the bold cliffs which stand before and on 



