1 



FAUNAL DIVISIONS OF EASTERN NORTH AMERICA. 213 



This forest is part of the old world forest of similar vegetation types Pinus 



Abies, Picea, Larix, Betula, Populus, and Alnus — which extends around the 

 northern land masses. Asia and North America were, as is well known, a con- 

 tinuous land in the Behring region. The development of this forest and its 

 extension may have been partly favored by the moist climate due to the melting 

 of vast masses of ice. Many of its faunal forms unquestionably extended their 

 ranges with its advance over the uncovered territory and are now co-extensive 

 with it; some forms seem to be indigenous to it in its American area (Zonotrichui . 

 PassereUa, J unco, Perisoreus, among birds), while numerous others have entered 

 it from the American region farther south. This forest may have been developed 

 in Mid-Pleistocene times, for the remains of numerous mammals of 

 species, as well as of certain extinct forms, representing forest, meadow, and 

 river types, have been found in deposits of this period in certain localities 



(6) The Deciduous Forest Type. — The broad-leaved hardwood forest of 

 North America is one of the most characteristic regions of the world. A marked 

 divergence from old world types, both in flora and fauna, is noticeable as we pro- 

 ceed southward from its northern limit. This forest has probably existed from 

 remote times, for the remains of such trees as the pin, white, and bur oaks, 

 {(Jucrcus palustris, Q. alba, and Q. macrocarpa), the beech (Fagus), the hazel-nut 

 (Corylus), the plum (Prunus), the hickories (Carya porcina and C. alba), the 

 thorn-tree (Crataegus), the Virginia creeper (Parthenocissus) , and the pitch pine 

 (Pinus rigida), have been found by Mercer in the deposits of the Port Kennedy 

 Cave in Pennsylvania. 2 These are all existing species found in a deposit of the 

 Mid-Pleistocene. It was probably developed in the unglaciated area and 

 spread northward, following the belt of coniferous forest that skirted the retreat- 

 ing ice-sheets. Some of its more northern trees have mingled with the conifers, 

 forming a mixed forest, quite characteristic of the borderland between the two 

 types along the northern tier of States and in southern Canada. No hard and 

 fast line of demarcation separates the faunas of these two forest types, there 

 being some penetration of various forms from either side. A number of species 

 of migratory birds do not extend their breeding ranges much beyond this decidu- 

 ous forest; such genera, for example, as Meleagris, Colinus, Zenaidura, Icterus, 

 Sturnella, Pipilo, Passerina, Zamelodia, Troglodytes, Toxostoma, Vireo, Piranga, 

 and Sialia. Various genera of lizards and snakes are limited to this deciduous 

 forest in their northward distribution — Sceloporus, Eumeces, Coluber, Carphophis, 

 Heterodon, Tropidonotus , Ophibolus, Cyclophis, Crotalus, and Ancistrodon. Rep- 

 tilian life as a whole is confined mainly to this forest in its northward dispersal, 

 and here temperature has possibly a more or less direct influence, although 

 the garter snakes (Eutainia) and the grass snake (Liopeltis) range well into the 

 coniferous forest. 3 



269-288. E. D. Cope, 



H. C. Mercer, Jour. Acad. Nat. Sci. P 

 froc. Acad. Nat. Sciences Phila., vol. XI, pt. 2, 

 mals, New York, 1910, p. 469. 

 * H. C. Mercer, ibid. 



xt i ' Arthur Erwin Brown, Post-Glacial N< 

 Mat. Sex. Phila., vol. LVI, pt. II, p. 464, 1904. 



F. Osborn, The Age of Mam* 



Acad 



