24 PROCEEDINGS OF THE ACADEMY OF [1897. 



deciduous trees, alternating with pines and occasional hemlock in 

 swampy localities, isolated bogs of tamarack and rhododendron and 

 fir affording retreat for animals more characteristic of the Canadian 

 fauna. 



The lakes of New Jersey are numerous ; Culver's Lake and Long 

 Lake together cover a considerable tract, and with their surround- 

 ings of swamp and mountain form a natural forest game preserve 

 that is well worth the future attention of the legislators of the State. 

 At Lake Hopatcong, the largest of all, the country is less mountain- 

 ous, and the fauna and flora shade somewhat into the Carolinian 

 elements, but at Greenwood Lake the western range of Greenwood 

 Mountain shows the most marked Canadian features noted in the 

 State, frequent swamps and bogs of white cedar, fir, pine, hemlock 

 and tamarack nestling among the depressions of the summits. 



The excursions of which the following pages form a summary are 

 part of the author's plan to make a comprehensive zoological survey 

 of all the counties of New Jersey and Pennsylvania, with special 

 reference to mammalogy and herpetology. About half of this labor 

 has been completed. 



1. Didelphis marsupialis virginiana (Kerr). Virginia Opossum. 



No specimens of opossum were taken. Its rare occurrence at 

 Greenwood Lake, where I was informed by the hunters that two 

 had been captured in the last two years, is of interest as showing the 

 presence of this animal in the most boreal surroundings which the 

 State affords. 



An examination of the large opossums of North and South Amer- 

 ica which belong to the marsupialis type of Linnseus, shows a spe- 

 cific difference in the character of the last premolar. In Brazilian 

 and Surinam specimens this tooth is a retrorse, blunt, rounded cone 

 with slight trace of a shoulder above the cingulum on the posterior 

 border. In examples from the eastern United States and Mexico 

 the tooth is sharply and abruptly conical, compressed laterally and 

 entirely surrounded by a tuberculate basal shoulder. Independently 

 of other marked characters, this is sufficient at once to divide spe- 

 cifically the composite group marsupialis as defined by Oldfield 

 Thomas 1 into two sections. A study of Linnaeus' description 2 leads 

 me to adopt Hernandez's Mexican animal as the least composite 

 type of marsupialis with definite given habitat. D. karkinophaga, 



^at. Marsup. Monot. B. Mus., 1888, pp. 323-327. 



-Syst. Nat., 1758, p. 54. 



