Cretaceous Fossils in Eocene of Maryland. — Bagg. 371 
specimens that they could not be distinguished from them if 
both were in the same tray. The Cretaceous marls which 
underlie the Eocene are at this locality on Western branch 
fully twenty feet below this level. Furthermore as these 
brachiopoda occur with such characteristic Eocene fossils 
as Ostrea compressirostra and Cucullgea gigantea there can be 
no question of the age of the deposit under consideration. 
The second discovery was made in the blufifs of the Poto- 
mac river not far from Clifton beach on the Maryland shore 
where a perfect specimen of Gryphsea vesicularis showing 
both valves was obtained. The shell is identical with those 
so numerous in the Rancocas marl bed of New Jersey. An 
examination of these Cretaceous fossils shows that their in- 
habitants lived in the waters at the time the Eocene green- 
sand was being deposited for none of the shells are water- 
worn in the slightest degree and the interior of the shell is 
filled with the same glauconite and sand grains of which the 
surrounding greensand is composed. In fact I not only be- 
lieve that these organisms lived side by side with their Eocene 
associates but that they existed under most favorable con- 
ditions as their large size and thick shells attest. 
A key to the explanation of their occurrence is, I think, 
to be found in the peculiar relation to the Terebratula and 
Gryphaea zones as they are developed in the state of Delaware. 
On the south bank of the Noxontown mill-pond their position 
is well seen. Throughout New Jersey these fossils occupy a 
constant position beneath the limesands of the Rancocas. 
A generalized section of the New Jersey Rancocas is as fol- 
lows: 
Thickness in Feet. Formation. Name. 
10-20 Limestone and Limesand. . Vincentovvn Limesand. 
2-3 Terebratula harlani i* Shell layers )c 11 
3-4 Gryphaea vesicularis \ of Cook. > nj.,„i^ 
5-20. Green Marl ) 
After crossing the Delaware river, although these beds 
continue southward, their position changes and we find the 
shell layers above the limesand. This is well seen along a 
large portion of the south shore of Noxontown mill-pond. 
If these limesands belong to the same period of deposition as 
