1889] 



MARYLAND ACADEMY OF SCIENCES. 67 



decreased to a thickness of less than ten feet, and rests at a level 

 of about ten to fifteen feet above the bed of the creeks. 



Exactly how far eastward the thick body of mixed fossiliferous 

 matter extends, we have at present no means of knowing. Nor 

 can we trace it southward for a great distance beyond the 

 boundary line of Charles county, in the country adjoining 

 Pomonkey Neck. As far as at present known, it runs from the 

 middle of the promontory reaching back from Fort Washing- 

 ton, is entirely cleared away by the erosion of Piscataway Creek, 

 and south of that stream passes into the high hills which are 

 cut by the brooks near Farmington ; while farther on it appears 

 exposed in the ravines and gullies adjacent to the boundary 

 of Charles county. It occupies intervals of a wide tract in this 

 region, but it no longer forms such thick deposits after the head 

 of the Piscataway estuary is reached. Possibly we may state, 

 with near approach to accuracy, that it occupies a large part of 

 an area which stretches about six miles from north to south by 

 five miles from west to east. This is the region which has thus 

 far furnished the largest proportion of fossil shells to collectors, 

 and here it is that the greatest number of yet unreported 

 species will reward the careful efforts of patient explorers. 

 Already about fifty species of fossil shells have been procured 

 from the numerous ravines of this tract of country ; and a few 

 of these appear to belong to horizons hitherto regarded as lying 

 far above the Claiborne inferior level to which most of the 

 fossils found here belong. 



It seems unlikely, after viewing such vast deposits of fossil 

 shells as those which confront the observer in this region, that 

 the short list here given should enumerate more than a small 

 proportion of the species buried in these huge mounds. Doubt- 

 less multitudes of other forms will yet reward the patient 

 collector in these piles of oceanic debris, and this is made more 

 evident by the many fragments of strange shells which are 

 turned out there by every excavation of the deposit. The 

 mixture of upper and lower Eocene species in these beds has yet 

 to be accounted for ; but as the upper Eocene forms have thus 

 far been found embedded only in confused materials, it is possi- 

 ble that they were out of original position. 



