Palcontological Speculations. — Gratacap. 225 
and the precursors of Chemung Hfe are found. But in both 
these cases we are evidently in the presence of oscillating con- 
ditions ; we have shown us again, what seems so universal 
and constant a predicament in the geological record, an extend- 
ing continental margin with a previous deeper sea life pushed 
away from the continental sediments and existing under stress 
and competition (See Chamberlin, Jour, of Geo!., \'ol. \ I, p. 
449.) in narrower precincts, itself surging back again upon 
the continental shelf, somewhat modified by its long absence, 
when the deeper water conditions supervene nearer the land 
surfaces. Yet if the shallow water character of the Marcel- 
lus and Genessee is conceded the presence in both of ammon- 
oids seems contradictory. Dr. Clarke ( 50th Ann. Rep. Re- 
gents, p. 137) insists that in the Genessee these goniatitic re- 
mains are "not a mechanical invasion, a congeries of flotation, 
but is in harmony with its components in mode and direction 
of derivation." Deferring a longer reference to that fact, and 
reverting again to the disappearance, sometimes partial only. 
of the lamellibranchs in the Marcellus and Genessee. we must 
conclude that the shallowing of the water was not an entirely 
determinate cause expelling them, but that some associated 
feature in the character of the water, or bottom, brought it 
about more explicitl}-. This feature may be the widely dissem- 
inated bituminous contents of these shales. There seems to 
be evidence that this bituminous matter was, to some extent 
at least, derived from the land and that it was disseminated 
through the water probably coincident with land storms, l^ring- 
ing on inrushes of fresh water, and overwhelming accessions 
of mud. 
It is well known that in the development of oysters, clear- 
ness of water, pemianence and hardness of bottom, still and 
undiluted marine conditions favor the survival of the voung. 
And this is also true of other bivalves. Mr. R. E. C. Stearns 
in his suggestions as to the best means of transplanting the 
edible bivalves, (Glycinicris, Sa.ridoimis. Schi.':othocnis) of the 
Pacific coast to the east, has stated that such conditions sliuuld 
be measurably secured, though in the case of some of these 
shells, slime, alluvium, drainage and refuse matter did not 
actually exterminate, or even diminish them. ( )f course the 
Marcellus conditions if unfavcjrable to an expansion of laiuel- 
