8 
LEA’S DESCRIPTION OF A FOSSIL SAURIAN 
elevated m their present irregular condition. But one or two Molluscs, it would seem, 
had been observed, heretofore, indicating their existence during the period of this 
formation. In a future portion of this paper I shall show that another did exist in the 
“ Potomac Marble.” 
It has been well known for a long time, that the calcareous conglomerates of this 
Red Sandstone formation, formed the North-Western border of it, with some interrup¬ 
tions and some changes in its composition, resulting from its derivative rocks. Thus 
we find it in Rockland County, in the State of New York, near to the New Jersey 
line; and Prof. Mather describes it under the name of “Red Conglomerate 
Limestone,” and states that “ it occurs at or near the junction of the red sandstone 
formation with the primitive rocks,” that it is composed mostly of pebbles and angular 
fragments of grey and black limestone, (like the adjacent limestone,) mixed with 
pebbles of quartz, granite, gniess, hornblende, sienite, &c.,and all cemented together 
by a reddish argillo-calcareous paste, mixed with gravel and sand of the various 
materials mentioned.” “ In its general aspect it is similar to the Potomac Marble.” 
He considers them “to be among the last formed rocks of the Red Sandstone division,” 
and formed of the beds of a limestone, of more ancient date in the vicinity, and “ near 
the ancient shore on which the attrition may have been effected.” 
Proceeding from the State of New York into New Jersey, we find these limestone 
conglomerates at Pompton, at Germantown, and at Spring Mills on the Delaware 
fifteen miles below Easton. In the New Jersey Reports, Prof. Rogers names it 
“ Variegated Calcareous Conglomerates,” and calls it a heterogeneous, though well 
characterized rock, which “ may be regarded as a distinct formation from the group 
of red shales and sandstones beneath it, being the result of a wholly different train of 
physical causes.” He considers it to constitute the uppermost member of the 
middle secondary series, overlying the red shale along its north-western margin, in 
insulated patches near the foot of the primary hills, (p. 135.) In its line south-west- 
wardly, I recognized this Calcareous Conglomerate on Ilassac’s Creek, in Upper 
Milford, Lehigh County, Pa., where Dr. Shelly found the interesting Saurian bones 
which he presented to this Academy, and which, in April of last year, I stated to be 
the fossil bones of a “ reptilian quadruped ,” which I proposed to call Clepsysaurus 
Pennsylvanicus .* hourglass.) From this point to the Schuylkill three miles 
below Reading, this rock may be observed in various places, and, where the Reading 
Railroad crosses it by a deep cut, it is exposed for nearly a mile, as a beautifully 
variegated limestone conglomerate, properly a breccia, so coarse sometimes in its 
materials as to present pieces quite eighteen inches in diameter. Continuing on the 
same line of direction, it crosses the Susquehanna at Bainbridge, and the Potomac 
south of Frederick, and there affords the “ Potomac Marble.” 
* Sec Proceedings of the Academy of Natural Sciences, 1851, pp. 171 and £05. 
