1914.] NATURAL SCIENCES OF PHILADELPHIA. 455 



IV. The Coastal Plain. 



The Coastal Plain includes all of the country south and east of the 

 fall-line. It consists essentially of a low plain of very sli,i>-ht relief 

 and hence, for most of its extent, at least, of very imperfect drainage. 

 This is especially true of that portion east and south of the range of 

 low hills marking the divide between the Delaware and Atlantic 

 drainage systems. In this part the seaward slope is exceedingly 

 gradual and consequently the stream flow is very sluggish and the 

 drainage very inadequate, resulting in the formation of extensive 

 bogs. West of the divide the stream gradient is considerably greater, 

 so that this part, constituting the Delaware Valley or Middle Dis- 

 trict of Stone, is on the whole fairly well drained, though in their 

 lower courses the'streams are so near tide-level that they become 

 very sluggish and form wide mud-flats through which the streams 

 tortuously meander. 



The all but universal soil of the Coastal Plain is a coarse sand 

 corresponding approximately to the Norfolk sand of the Bureau of 

 Soils. Associated with this are frequent areas of coarse gravel 

 similar to the Sassafras gravelly loam of the same Bureau.^- East 

 of the Delaware-Atlantic divide these sands and gravels form a 

 practically unbroken cover, but west of that line, in the Middle 

 District, they are frequently interrupted by more or less extensive 

 areas of clays and loams, some of which are due to the exposure of 

 the underlying Cretaceous and Miocene deposits consequent upon 

 the removal by erosion of the original capping of sand and gravel. 

 In consequence of this variety of soil types, the Middle District is 

 characterized by a greater diversity of flora and fauna than the 

 remaining subdivisions of the New Jersey Coastal Plain. 



The two general features in which the Coastal Plain most markedly 

 differs from the Piedmont Region are: (1) the almost universal 

 presence of coarse sands, and (2) the development of extensive tracts 

 of permanently wet areas. With these is correlated the prevalence 

 of two widely different types of fauna, a xerophilous fauna charac- 

 teristic of the sandy districts and a hygrophilous fauna characteristic 

 of the bogs and marshes. The inesophilous fauna is of relatively 

 limited extent, being fulh^ represented only on the clay and loamy 

 soils of the Middle District, but tending to spread into the other 



12 For the characteristics of these different types of Coastal Plain soils see 

 Soil Survey of the Salem, N. J., Area, Field Operations of the Bureau of Soils, 

 1901. 



