ere Se: 
72 General Notes, [ January, : 
THE GEOLOGY oF CHESTER County, PENNSYLVANIA.—Some 
points in the geology of this region of considerable complexity 
have been recently worked out by Dr. Persifor Frazer, of the 
State Geological survey. The results are published in his These 
Premiére presented to the University of France, 1882. The - 
structure of the limestone valley of Chester has long been under 
discussion. The northern hill is composed of sandstone and 
quartzite, the bottom of the valley of limestone, and the south 
hill of hydromica-and chlorite schists and slates. The first two 
formations are the primordial and auroral, Nos. 1 and 2 of Rogers, 
or the Potsdam and Calciferous of Hall. The dip of these beds 
is south-east, and there is no reversed dip and no synclinal. 
Professor Fraser believes that a fault extends along the northern 
base of the south hill for forty miles, and that the oldest beds - 
have been thrust up to form the south hill. The schists then are 
older than the Potsdam beds. Their dip is like the latter, south- 
east. South of this hill the schists descend and are succeeded by 
another limestone, which is in place between the former and the 
Potsdam beds. This formation is then considerably older than — 
the limestone of the valley. Fraser calls it the Doe-run lime- 
stone. This is succeeded by the Potsdam again, and it in turn 
by the valley limestone, as in the valley itself. This latter bedi 
appears in the region of Avondale and London Grove. 
KOWALEVSKY ON ELASMOTHERIUM.—Dr. W. Kowalevsky bas 
pees It is proven that Srorecires Duv. is identical with mek 
motherium. The genus stands at the top of the family. next t 
A The £. żypus was as large as the Indian rhinocert 
ope. 
Two New Genera oF PyrHonomorpHa.—M. L. Dollo, in. th 
Bull. du Mus. Roy. d’Hist. Nat. de Belgique, describes the Mo- 
sasaurian remains in the Museum of Brussels. He forms from cl 
He also proposes the genus Plioplatecarpus for the reception 
a Mosasaurian resembling a Liodon, but which in the structure 
its coracoid and maxillary teeth differs widely from that gef 
