THE AMERICAN MIDLAND NATURALIST. 



Ronkonkema — which is 410 ft. above the sea at High Hill, 

 Huntington. It is considered to be the older of the two, since 

 at places it is buried beneath the first. These two conspicuous 

 morainal ridges form the backbone of the areas previously 

 indicated, and each is a direct continuation of moraines of 

 Wisconsin age which are traceable from the Rocky Moun- 

 tains to New Jersey to Long .Island, Nantucket and Cape 

 Cod. East of Huntington, the moraines diverge more and 

 more and enclose broad, sub level tracts. The coastal 

 region, however, is comparatively level, with an elevation 

 above sea level ranging from less than 50 ft. over the great- 

 er part of Long Island. 



The glaciers invaded Long Island more than twice, for 

 certain deposits of clay and gravel and sand show that 

 there were advances of the ice even before the Ronkonkema 

 moraine was formed. Most of the material composing the 

 bluffs along the north shore and inlets is thought to have 

 been laid down by this earlier ice sheet.* The eastern ter- 

 minus of each moraine gives character to that end of Long- 

 Island and encloses a large body of water known as Pe- 

 conic Bay. The Ronkonkema moraine is remarkable for the 

 large body of water it encloses, Lake Ronkonkema, visited 

 yearly by the botanical classes at the Laboratory. This is 

 in a former glacial kettle hole, and is by far the largest 

 lake on Long Island, attaining a depth of 80 ft., and ex- 

 tending to about 25 ft. below sea level. Both moraines bear 

 the usual marks of terminal accumulations formed by the 

 continental ice sheet. Their surfaces are deeply pitted by 

 large and small kettle holes and depressions. Upon the 

 floors of some of the enclosed depressions lakelets or 

 swamps occur, and all others are distinctly moist, but by 

 far the larger number are without standing water. Large 

 portions of both moraines are composed of till of rather 

 typical composition, but there are extensive localities where 



* Dr. Ernest Antevs in a letter to the writer dated March 5, 1925, 

 reports the finding of varied clay (the summer and winter deposits 

 of glacial waters) at Glen Head, L. I., a few miles east of Great 

 Neck, at a brick yard one-half mile east of the station. He adds 

 that varves. (each of which represents one year of the glacial retreat), 

 may be expected here and there on the northern coast as exposed. 



