Fig. 16.—Section across Potomac River near Big Pool, Maryland. Shows gravel-covered terraces. Folio 179, U. S. Geol. Survey.
Beginning at the southern extremity of Maryland, we notice the occurrence of remains of Mammut americanum at or near St. Mary’s City. Other remains of the same animal have been secured near St. Clements in St. Mary’s County (p. [112]). Both of the localities are situated on territory mapped by Shattuck as Wicomico; but as remarked on page [112], our knowledge of the conditions under which the fossils were found is not sufficient to allow us to say more than that they belong to the Pleistocene. The species existed from early to late Pleistocene and can not be used to determine the age of the deposits.
Along Patuxent River, in Charles County, not far from Benedict, Cope (Proc. Acad. Nat. Sci. Phila., 1867, p. 155) recognized jaws and teeth of Grison macrodon and of Tagassu lenis (p. [220]). Both are extinct species.
According to Shattuck’s map of 1906, this region is covered by the Talbot formation; but inasmuch as the species named were obtained from pits furnishing Miocene marl, one can not be sure that they are not older than the supposed Talbot. It would probably require a search in the land records in order to determine exactly where the objects were found. The presence of Elephas primigenius suggests that this animal had been pushed down here during one of the glacial stages.
Nearly a hundred years ago an elephant tooth (p. [154]) was found somewhere in Queen Anne County, but it would probably be now impossible to determine the locality. In case the elephant tooth was found near Chesapeake Bay, as is very probable, there is no record of any Pleistocene vertebrate having been found in the central and eastern parts of the eastern peninsula.
In the eastern peninsula remains of Pleistocene vertebrates have been recorded from only two localities, Oxford Neck, Talbot County, and an undetermined locality in Queen Anne County. From Oxford Neck, Cope (Proc. Amer. Philos. Soc., vol. XI, 1869, p. 178) reported Elephas primigenius, E. columbi, Cervus canadensis, Odocoileus virginianus, Chelydra serpentina, and Terrapene eurypygia.
At Chesapeake Beach, William Palmer, of the U. S. National Museum, discovered a few remains of Pleistocene vertebrates. One of these is a tooth of an undetermined species of Bison, probably not the existing one. Another species is probably Equus leidyi (p. [189]). Three teeth appear to represent the peccary Tagassu lenis (p. [220]). In 1921, Dr. Adolph H. Schultz, of the Johns Hopkins Medical School, presented to the U. S. National Museum another specimen of T. lenis which he had found at Chesapeake Beach. Inasmuch as the fossils were picked up after having fallen from their resting-place, it is impossible to say to which formation they belonged. In the opinion of the writer, none of the three species indicates a late Pleistocene time.
On the opposite side of the western peninsula, at Marshall Hall, Charles County, there was found long ago a tooth which the writer refers to Equus leidyi.
Coming north into the District of Columbia, we find recorded the discovery of remains of horses and possibly at two different times. According to Darton’s work (Folio 70, U. S. Geol. Surv.), there is some later Columbia laid down along the route of the Chesapeake and Potomac Canal above Georgetown. This would now doubtless be regarded as belonging to the Talbot. It seems to follow that either the Talbot is much older than has been supposed or that some of the extinct horses continued on until a comparatively late time in the Pleistocene.
Within the limits of the city of Washington there has been found a tooth of probably Elephas primigenius at a depth of 35 feet, in the Wicomico formation (see p. [178]). On any theory of the origin of the terraces, the presence of the tooth at that depth in the ground and at that elevation appears to indicate a considerable geological age for the animal. To what extent materials may have been washed down from the surrounding higher land may be difficult to determine.