372 The American Geologist. December, i898 
in New Jersey, and there is no doubt but that they do, then 
we must conclude that the Terebratulse and Gryphaege mi- 
grated southward as conditions became unfavorable for their 
existence in New Jersey and continued to survive in later time 
in Delaware. The development, however, of both the lime- 
sand and the shell-layers becomes diminished farther south 
and before reaching the Chesapeake bay become so greatly 
reduced that the beds are only occasionally observed and it is 
doubtful if they exist at all in portions of the l^elt. The shell- 
lavers do occur on a branch of the Sassafras river called Swan 
creek on Mr. Jacob's farm. Upon the west shore of Chesa- 
peake bay only one locality has heretofore been known where 
the Terebratulge occur and this was mentioned by professor 
P. R. Uhler many years ago. The spot where professor Uhler 
discovered this brachiopod was at the base of the oxidized 
greensand blufifs opposite Annapolis. In place of the limesand 
and the shell-layers we find that the Rancocas formation in 
Maryland consists largely of glauconite grains and finely tri- 
turated sands which are more highly oxidized than the sands 
of the same formation in New Jersey. Furthermore, the glau- 
conite is not so abundant, and in Maryland this bed has been 
dug for fertilizer in only a few places. 
The writer's discovery of these fossils in Prince George's 
and Charles counties proves that these organisms not only 
continued their existence in the Eocene but that they mi- 
grated much farther southwest than has previously been sup- 
posed. Brachiopoda are rare in the Eocene of the Atlantic 
Slope and have never been recorded as occurring in Mary- 
land. Even in New Jersey Cretaceous where such a wealth of 
mollusca exists only two species of brachiopoda are at all plen- 
tiful. These forms are the one under discussion and Tere- 
bratella plicata Say. The latter is a small form and occurs 
widely distributed throughout the Monmouth formation, be- 
ing present in the Navesink marl bed and the Redbank sands. 
Terebratula harlani is, on the other hand, one of the largest 
and most beautiful of the genus found in America. Prof. R. 
P. Whitfield in his monograph of the Cretaceous Mollusca 
of New Jersey states that the shell has been obtained from 
