16 TRANSACTIONS OF THE ' [1888 



to the others, specimens of single valves having been found 

 with the shelly layers almost intact and the nacreous coating 

 still apparent. As yet, however, no thick and continuous 

 layers of the former, nor of the Terebratulae, such as are 

 common to the corresponding strata extending across the State 

 of New Jersey, have been found on the Western Shore of Mary- 

 land. Possibly this is owing to the neglect of the farmers of 

 this part of the State to dig the marl for use in agriculture. 

 We find that in but few places have the beds been deeply 

 excavated, and these have been chiefly in the vicinity of the 

 Patuxent and Potomac rivers, in the upper portion of Prince 

 George's county. Some deep wells on both sides of the Round 

 Bay region have penetrated far down into the black marl, or 

 even passed through it to the white sand beneath, but in no 

 instance has the well-digger reported the presence of compact 

 shell-layers in the strata passed through by his boring. 



The Cretaceous formation is not of uniform character through- 

 out its full extent in the State of Maryland. Like all the 

 other sedimentary deposits of the Atlantic coast plain, it has 

 brought together more aluminous, micaceous, or siliceous 

 matter in some areas than in others. It seems to have been 

 laid down in a region where the ocean penetrated into bays, 

 gulfs and estuaries deep enough to admit the growth of truly 

 marine forms of life, while at the same time a luxuriant flora 

 decorated the low hills, ridges and promontories which bordered 

 the shores. Likewise, lowlands must have entered between the 

 hills, into which extensive swamps pushed back into the adjoin- 

 ing country. Willows, conspicuous for their size, and bearing 

 remarkably large leaves, spread their branches over the water 

 in the drains. Pine trees of huge proportions grew on the low 

 sandy slopes. Magnolias decorated the marshy borders of the 

 tide-channels. The sassafras flourished on the stiif soils of the 

 open levels, and the viburnum-like bushes grew on the rich 

 loamy hillsides and in the ravines. Incalculable numbers of 

 these vegetable tenants of the soil were thi'own down or washed 

 into the deep black muds of this region, and their fragments, 

 charred and soiled by the accumulations of carbonaceous debris, 

 now rest in huge piles at the bottom of the marl mounds. 



