orioles, the common dove, and the bob-white or quail do not breed beyond its northern boundary. The brook trout does not range south of this fauna, and the rattlesnake, the copperhead, the puff adder, the green snake, the milk snake, and the water snake are not found beyond its northern border.
The Carolinian fauna is a distinctly southern type and characterizes the upper austral zone, which includes that portion of the coastal plain region that reaches from the foot of the Appalachian highland to the "fall line" of the various Atlantic streams. The northern limit of this fauna thus coincides with the inland border of the coastal plain which we have already referred to and which may be looked upon as the true dividing line between the North and South. The presence of such birds as the cardinal, the yellow-breasted chat, the Carolina wren, the tufted titmouse, the Acadian flycatcher, and the blue-winged, Kentucky, and worm-eating warblers during the breeding season is a sure sign of the Carolinian fauna. These species never go beyond its northern limits. Moreover, such species as the brown thrasher, the wood thrush, the house wren, the chewink, the dove, and the field sparrow, which find their northern limit in the transition zone, are far more abundant in the Carolinian region, and might almost be regarded as representatives of its fauna.
It becomes a matter of profound interest, not only to the ornithologist and the student of geographical distribution, but to every one who has in his heart a love of woods and fields, to locate this natural boundary by such fine shadings as the nesting place of a bird or the habitat of a forest tree. Let us take that portion of the line that cuts off a small corner of southeastern Pennsylvania. To the ordinary observer this special tract of country presents no marked difference from the landscape a hundred miles or more to the north or south of it. Its detail of features is quite similar and seasonal changes follow much the same course that they do in northern Virginia and southern New England. To the northwest, beyond the low, irregular ridge of the "upland terrace" that marks the gneiss and schist rocks of an ancient shore line, the country breaks into the rolling hills and dales of the interior uplands. To the southeast lies the flat lowland of the Delaware plain, and beyond this the pine barrens and marshes of the Atlantic coast plain of New Jersey. One who has an eye for the woods, however, will note a certain change in the trees from southern New England and the highlands of the Middle States. Groves of tall tulip trees, with their broad, smooth leaves of shining green and large, creamy blossoms streaked with orange that open toward the end of May, form a characteristic feature of the woodland scenery. The sassafras and the persimmon are scattered more or less abundantly through the woods
