190 LEA'S DESCRIPTION OF A FOSSIL SAURIAN 



elevated in 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 divi.sion," 

 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 Hassac'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 

 Pennsijlvanicus.* (jr?.f4u5^a, 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." 



* See Proceedings of the Academy of Natural Sciences, 1851, pp. 171 and 205. 



