152 THE AMERICAN NATURALIST. (Vol. XXXIII. 
in the gravel pits along the railway may be accounted for by 
the same hypothesis advanced by Dr. Abbott to explain the 
position of the rude implements in that locality. The railroad 
cutting passes through an old channel of Assunpink Creek, 
and Dr. Abbott states that “it was always along the old creek 
bed that the chipped argillites were found, along the railroad 
excavations east of the site of the gas works where the skull 
was found; and when the excavations continued beyond the 
FIG. 9. 
area of the immediate creek valley they disappeared.” ! The 
thickness of the Trenton skull is not rare in American crania. 
The Delaware skull, No. 48,974, furnishes an example close at 
hand of an even greater thickness. 
The Burlington and Riverview skulls are thin and fragile, 
and their sutures are open (Figs. 7, 8). They are unworn and - 
present no evidence of ever having been moved by flowing 
water, torrential or otherwise. They do not closely resemble 
the Trenton skull, though the morphological differences are 
1 In a letter to the writer, December, 1898. 
