Agassiz— Paleontological and Embryological Development. 375 
antedate the era of the rem and these broad and 
ongly marked valleys were a he sea in that er 
stretching a third —— a cae of the weg across the Putnam 
County Highland re n these extensive bay the lime 
and quartzyte, were formed. Since, also, the limestone now in 
these valleys is what is left after long ages of denudation, it has 
but a small part of the — and thickness which belonged 
originally to the format 
m the fact of this: ‘prosdicionds of the Archean High- 
lands, we appear to have also a reason for the contortions of 
the rocks in the northern half of Westchester County, and for 
the nearly east-and-west courses in the bedding. For in the 
upturning or flexing of the strata, which took place, and 
which put the beds in nearly vertical positions over the whole 
county, the Archean stood as a stable barrier on the north ; 
against it the rocks were forced a the lateral pressure 
that produced the great results.) The mass of the Archean 
as here an easterly trend, much more easterly than that of the 
New Jersey Archzean, although the strike of the Archian 
beds is generally northeast." The direction of the pressure and 
the resistance to movement in such a barrier, are the chief of 
the conditions that would have determined the direction of the 
folds, fractures and faults in the disturbed strata. 
[To be continued. ] 
* 
Art. XL. a Re and Embryological Development. Ad- 
dress by ALEXANDER Aaassiz, Vice-president of Section B, 
-at the recent ices Meeting ‘of the American Association 
for the Advancement of Science. 
[Continued from page 302.] 
up now the embryological development of the 
veal ‘families which will form the basis of our comparisons, 
beginning with the Cidaride, we find that in the earliest stages 
they very soon assume the characters of the adult, the changes 
being limited to the development of the abactinal system, 
increase in number of the coronal plates, and the modi fications 
of the Pes OY pee primar les. 
I the changes undergone by the young 
are limited to ie “gfeaal transformation of the embryonic 
Spines into those which characterize the family, to the changes 
*4 In New Jersey, also, the trend of the mass of the Archean has more isn 
according to Prof. G. H. Cook, as brought out in his New Jersey Geological Re- 
port (1868), than re stike of its beds, the former being about northeast and the 
tter north-northea 
