492 
PALAEONTOLOGY OF NEW-YORK. 
CATALOGUE OF SPECIES, 
AND NUMBER OF INDIVIDUALS OF EACH, 
OBTAINED FROM THE SHALY LIMESTONE OF THE LOWER HELDERBERG GROUP, 
AT A SINGLE LOCALITY IN ALBANY COUNTY*. 
The collection of fossils from the Lower Helderberg rocks was begun in 
Albany county, and elsewhere, in 1843. In many localities the shaly 
limestone of this group is of such a character that it decomposes on its 
outcrop; while the fossils, being silicified, remain uninjured, and are found 
among the fine debris along the slope of the escarpment. I engaged the 
service of persons living upon the ground, mostly of children who were 
able to collect from the ploughed fields and elsewhere along this outcrop. 
The area from which collections were chiefly made does not exceed a 
quarter of a mile in width by half a mile in length, though a small number 
of specimens may have been obtained at a greater distance. The specimens 
collected for a period of about three months were turned over, without 
counting, to Mr. Seaman of Paris, who was then travelling and making 
collections in this country, and are not included in the number specified 
in the following lists. 
During the time from 1853 to 1857, the collections were not as con. 
stantly continued : fewer persons were engaged, the work being expen¬ 
sive ; and having already all the species likely to be obtained, I did not 
press the collections as before. 
During the years 1857 and 1858, large numbers of specimens were 
obtained from this locality : every new ploughing of the ground turns 
up a fresh crop of these fossils, and the locality is still very prolific. 
Of the little Orthis varica, great numbers may still be obtained; and 
* Some years since, I prepared this schedule, as far as the collections had then been made, to communi¬ 
cate to Prof. Edward Forbes, under the title of the results of “ Dry Dredging”, in acknowledgment of 
some papers on dredging sent me by that eminent and lamented naturalist. The news of his death prevented 
the communication from being sent; and I have recently added the results of later collections, and present 
it in this form, which may have some little interest, both to naturalists who are dredging in the present 
ocean, as well as those who are collecting the fauna of an ancient sea. 
