1894. | NEW YORK ACADEMY OF SCIENCES. 125 
there is little true bowlder till, large bowlders are scarce and clay 
isabsent. Most of the morainal material is more like coarse water- 
worn gravel, quartzose and granitic in composition, with numer- 
ous fragments of triassic sandstone. Further westward both the 
amount of till and the number and variety of the large bowlders 
increases. Shales and limestones begin to be represented among 
them and calcareous pebbles enter into the composition of the 
gravels. On Oak Neck I found a bowlder, containing Spirifera 
macropleura and Strophomena radiata, referable to the Helder- 
berg. 
Asarule the cretaceous drift material seems to accompany 
the bowlder till and where the latter is absent the former is 
absent also. Or perhaps it would be better to say that where 
bowlder till is well represented is where we may expect to find 
the cretaceous drift material in greatest abundance. 
One other element remains to be considered, viz: The gravels 
which presumably represented the pliocene or pleistocene de- 
posits of the coastal plain. These are recognized as the “yellow 
gravel” or ‘“ pre-glacial drift” of New Jersey, and they occur 
mixed up in the moraine both there and on Staten Island, The 
determination of their occurrence on Long Island would 
largely depend of course upon the ability to recognize and dif- 
ferentiate them from other gravels, and this is not always an easy 
matter to accomplish. Lithological characteristics are of little 
value, and color can not be depended upon, as the prevailing 
yellow color is dependent upon the action of ferruginous waters, 
which gives them a more or less superficial coloring of the oxide, 
and this may be, and often is, reduced by the action of decaying 
vegetation, so that the gravels again appear colorless. 
Practically the only characteristic which can be relied upon 
is the presence of silicified paleeozoic fossils. These have served 
as criteria for the identification of the “yellow gravel ” wherever 
found, and hence I maintained a close search for them in all the 
gravel accumulations, whether stratified or unstratified. 
Proceeding westward from Northville I first found these fos- 
sils on Lloyd’s Neck. From thence to Glen Cove, however, they 
were quite abundant. Many of them are not thoroughly sili- 
cified, and their origin from former calcareous rocks is quite 
apparent. At times they are white, again they are character- 
istically yellow, the color or its absence seeming to be merely 
incidental and dependent upon the causes previously indicated. 
At Glen Cove there are great accumulations of white sand and 
gravel accompanying the cretaceous clays, the whole series 
much contorted by glacial action; but as many of the pebbles 
contain the characteristic silicified fossils we can but consider 
