Clifford Clays and the Matazvan. — Knapp. 2J 
There is no objection to making the Matawan include th^r 
CUffwood clays so long as it is kept clearly in mind that the 
Cliffwood clays are Raritan. But the CUffwood clays must not 
be spoken of as the equivalent of the Crosswicks clays and the 
flora of these laminated sands and clays at Cliffwood must not 
be confused with the fauna of the Crosswicks clays. And th.- 
fauna from the Merchantville marly clay at the top of the Cliff- 
wood cliff must not be confused with the flora of the clays and 
sands beneath. 
The clay report of the New Jersey geological survey, 1878, 
page 75, reads, "The green sand of the Clay Marl seen in th-^ 
cuts of the N. Y. & Long Branch R. R. near Cliffwood road 
and station marks the southeastern limit and top of the plastic 
clay series (Raritan)." 
A glance at the map shows that this throws all the Cliff- 
wood clays into the Raritan and shows, when taken with the 
context, that the writer of the '78 report clearly recognized thv 
Cliffwood clays and definitely referred them to the Raritan. 
Faunas and floras are supposed to be aids to correlation : 
it might not be imperinent to inquire why the Cliffwood clay? 
were not referred at once to the Raritan on paleobotanical ev- 
idence when sixty-four per cent of the species were identical 
with the Woodbridge flora and still others were identical with 
species found in the Raritan of Staten Island, Long Islana, 
Block Island, and Martha's Vineyard. 
It is disconcerting to the stratigraphist when the paleobot- 
anist and paleontologist refuse to follow their own guides. 
Trenton, N. J. 
BITUMEN AND OIL ROCKS. 
By G. C. Broadhead, Columbia, Mo. 
Bituminous, or asphaltic, rocks owe their condition to the 
presence of the oil with which they are saturated. These oils 
are various forms of what is commonly called petroleum. 
Hydrocarbons include marsh gas. the light gases formed in 
mines and flowing from deep wells, thin oils, as petroleum, 
thick oils as maltha and bitumen or mineral tar, asphalt and 
the various coals. Where oil and tar springs prevail, the rocks 
