4»« palj:ontology of new-york. 



CA.T^LOaXJE OF SPECIES, 



AND NUMBER OF INDIVIDUALS OF EACH, 



OBTAINED FROM THE SIIALY 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 yeftra since, I prepared this schedule, as far as' the collections had then been made, to communi- 

 cate to Prof. EnwAKT) Forbes, under the title of the results of " Dry Dredging", in acknowledgment of 

 some papers on dredging sent me hy that eminent and lamented naturalist. Tlie 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. 



