1914.] NATURAL SCIENCES OF PHILADELPHIA. 481 



tion. In this region neglected fields are occupied by a weed vegeta- 

 tion similar to that occurring in similar situations in the Coastal 

 Strip, and this is correlated with the presence of similar species of 

 Orthoptera, the more important species being the following: 



Syrhula admirabilis Melanoplus femur-riihrum 

 Orphulella pelidna " femoratus 



Arphia xanthoptera Scudderia curvicauda 

 Chortophaga viridifasciata " furcata 



Hippiscus rugosus Amblycorypha uhleri 



Dissosteira Carolina Conocephalus rohustus 

 Psinidia fenestralis (local, on bare " triops 



sandy spots) Orchelimum vulgare 



Melayioplus atlanis Xiphidium strictum 



Summary. 



1. In the region covered by eastern Pennsylvania and New Jersey 

 two strikingly different types of Orthopteran faunas are exemplified, 

 namely, a Transition fauna in eastern Pennsylvania and northern 

 New Jersey and an Upper Austral fauna in southern New J-ersey. 



2. In this region the Transition fauna coincides in distribution 

 with the Appalachian Mountain System and the Piedmont Plateau; 

 the Upper Austral fauna with the Coastal Plain. 



3. It is not possible with the data at present available to give a 

 complete causal explanation of the observed facts of distribution as 

 exemplified by the Orthoptera of this region. 



4. Atmospheric temperature alone does not afford a satisfactory 

 explanation of the facts of distribution; more pertinent is the tem- 

 perature of the medium in which or on which the organism, or any 

 stage of the organism, dwells. The areal distribution of an organism 

 is probably a resultant of the interaction of a number of factors and 

 not of any one single factor. 



5. In the region included in this study the striking differences 

 between the biotas of the Piedmont Plateau and the Coastal Plain 

 are closely correlated with equally striking differences in topography, 

 drainage and soils. 



6. The Piedmont Plateau is a region of considerable elevation and 

 good drainage. Permanently wet areas constitute a relatively insig- 

 nificant feature of the region. 



7. The Coastal Plain is a region of very slight elevation and usually 

 poor drainage. Permanently wet areas constitute highly important 

 physiographic features of the region. 



8. The soils of the Piedmont Plateau are loams of residual origin. 



