J. Hail on the Fossils of New York. 245 
others of similar type, yet our daily experience proves to us the 
truth of this principle as shown in the organized remains of suc- 
cessive strata. 
Mr. Hall remarked that, when a few years since he maintained 
that the single genus Catenipora would be found typical of cer- 
tain strata, and a reliable guide from New York far to the west o 
the Mississippi, the idea was regarded as absurd and was absolutely 
ridiculed. Now he was happy to say to the Association, that oth- 
er observers than himself had volunteered to sustain that opinion, 
and the Catenipora was regarded not only here but in Europe, 
as marking unequivocally a certain stage in the system, never ap- 
pearing in the lower Silurian or rising into the onian. Both 
-de Verneuil and M. Roemer had confirmed this opinion by ex- 
tensive observations in the United States. If then, a single spe- 
cies of coral is so limited in its geological range, what may we 
hot expect from other remains of higher organization ? 
ev 
Sand miles in extent, and the same remark might be applied 
to other species more or less conspicuous in every part of the 
Series, 
As an example of a fossil supposed to have a wide geological 
range, he instanced the F'avosites lycoperdon of Say,—Cheetetes 
are represented by D. macropleura—D. crispus, which is repre- 
sente 
represented by a larger species with similar marking. ‘The small 
D. biloba of the Niagara group, is represented by a similar pecu- 
liar form in the shaly limestone, which is nevertheless distinct. 
"M.deV i the D. biloba of the Wenlock formation of Europe, as 
identical arith thos oe z Dolthyris shaly limestone of the Helderberg. ‘This 
may be true, but our Niagara species appears to us to be quite distinct. 
