FREE INSTITUTE OF SCIENCE 



37 



THE LIFE FEATURES OF THE COASTAL PLAIN AND THE PIEDMONT 



bringing a wider and wider area of the Piedmont within the realm of the Caro- 

 Hnian fauna. This accounts for the greater abundance of some of the above- 

 mentioned species among the hills of the Piedmont in southern Chester and 

 Lancaster counties and the lower Susquehanna watershed. 



Certain other birds are typical of this CaroHnian region about Philadelphia 

 — the Yellow-breasted Chat {Icteria virens), the Acadian Flycatcher {Empi- 

 donax virescens), the Cardinal Grosbeak {Cardinalis cardinalis), the Barn Owl 

 {Aluco pratincola), and the Turkey Buzzard (Cathartes aura) are all increasingly 

 more abundant in the south. It is a noteworthy fact that some of the above- 

 mentioned species, as the Cardinal, the CaroHna Wren, the Carolina Chicka- 

 dee, and the Tufted Titmouse, are resident birds throughout the year, wintering 

 along this northern border of the CaroHnian fauna in the region about Phila- 

 delphia. In former years the Mockingbird {Mimus polygloUos) appears to 

 have been much more numerous than at the present time and to have wintered 

 in this vicinity. Among mammals the gray fox and the opossum, character- 

 istic austral species not ranging to any extent beyond the Kmits of the Caro- 

 linian fauna, are much more numerous on the Coastal Plain lowland, the former 

 being rarely found in the hill country. The distribution of certain reptiles in 

 like manner indicates this region of the lower Delaware Valley to be more or 

 less distinctly of the nature of a faunal barrier. The common Box Turtle 

 {Terrepene Carolina) that we meet with so frequently in our woodlands is a 

 characteristic austral type, and the same may be said of the Ground Lizard 

 {Leiolopisma laterale) and the Httle, active Swift Lizard (Cnemidophorus). 

 The celebrated "Diamond Back" Terrapin (Malaclemmys) and the Red- 

 belHed Terrapin (Pseudemys) do not range north of the Carolinian fauna. 

 Muhlenberg's Tortoise (Clemmys) is curiously local in east Pennsylvania and 

 southern New Jersey. Among snakes the Corn and the Chain Snakes (Lampro- 

 peltis), the Water-Snake {Natrix sipedon erythrogaster) , and the Pine Snake 

 (Pituophis) are limited northward in the same way, while the Copperhead 

 (Ancistrodon contortrix) is rare north of this faunal boundary. In the same way 

 the httle Green Snake (Opheodrys aestivus) appears to be more or less Hmited in 

 its northward distribution. 



Ill 



The question of the distribution of these Carolinian types turns on the 

 factors that are involved in thus hmiting their northward ranges. Tempera- 



