1889. | NEW YORK ACADEMY OF SCIENCES. 53 
group of rocks, and had been able to detect no unconformability 
at any point among them. He thought it probable that most 
of the crystalline limestone outcrops were actually the same beds 
brought repeatedly to the surface by the folding, faulting and 
pitching of the strata. Rocks similar to, if not entirely identi- 
cal with, the hydromica schists shown by Mr. RAND occur in 
very considerable development about the eruptive masses of 
Verplanck’s Point and Stony Point, where they are evidently 
altered Paleozoic beds, and such may also be studied along the 
western margin of the Triassic area at various points in New 
York and New Jersey. 
Mr. Kunz, Mr. Wm. Niven, Dr. Britton, Pror. MARTIN, 
Dr. FRIEDRICH, and the PRESIDENT continued the discussion 
on a number of points, comparing the rocks and minerals of 
New York, Westchester Co. and Staten Island with those de- 
scribed and shown by Mr. Ranp. A selected series of one hun- 
dred typical specimens of Philadelphia rocks had been brought 
on by Mr. RAND, to illustrate his paper. This interesting col- 
lection he generously offered to the Mineralogical Section of the 
Academy, to be retained in New York; and the gift was ac- 
cepted, with a vote of thanks to the donor. 
Dr. J. J. FRIEDRICH presented the following: 
RESUME OF THE LITHOLOGY OF MANHATTAN ISLAND. 
{Nomenclature and classification according to E. Kalkowsky’s 
“« Elemente der Lithologie,” Heidelberg, 1886.) 
Among our local rocks we find representatives of the following 
eleven groups: 
1. Dolomite. 
2. Serpentine to Peridotite Group. All varieties found in 
Staten Island occur here; especially ophiolite, in fine specimens, 
deserves mention. 
3. Tale and Chlorite Group.—Especially a protochlorite schist 
in contact with pyroxenites. 
4, Granulites.—Garnetiferous, amphibolitic, marcasitic, and 
micaceons. 
5. Quartzite. 
6. Pyroxenite. 
7. Epidote. 
