PRELIMINARY NOTICE 



OF THE LAMELL1BRANCHIATE SHELLS OF THE UPPER 



HELDERBERG, HAMILTON AND CHEMUNG 



GROUPS. 



[Preparatory for the Palaeontology of New York.] 



Paet 1. 



The fossil Lamellibranchiata of the higher groups of the New York 

 geological series are often abundant, of great variety of form and of 

 very interesting character. Our earlier knowledge of these fossils is almost 

 wholly due to Mr. Conrad, who described eleven species in the Annual 

 Report of the Geological Survey in 1838; and during the following years 

 this work was continued, both in the Annual Reports of the Survey and in 

 the Journal and Proceedings of the Academy of Natural Sciences of Phila-. 

 delphia. The total number of species described by Mr. Conrad from all the 

 groups is about one hundred and ten, and fifty of these have been illustrated 

 in the publications of the Academy. The number of species at present known 

 from the same formations is about six hundred, of which nearly five hundred 

 are from the groups above the Oriskany sandstone. 



During and since this period the writer has made extensive collections of 

 these fossils, both with his own hands and through the agency of his assistants, 

 preparatory for publication in the Palaeontology of New York. After having 

 accumulated considerable collections, and feeling the importance of their 

 proper identification, I engaged Mr. Conrad to examine the whole and to give 

 his determination of the species which he had described. On three several 

 occasions, previous to 1865, Mr. Conrad visited Albany for the express pur- 

 pose of making these determinations and identifications, labeling one or more 

 of each of those which he recognized as typical forms of the species. Through 

 these means, and by later study and comparison, it is believed that nearly all 

 the previously described forms have been satisfactorily determined. 



In 1869 the writer printed and published " Preliminary Notice No. 2, of 

 the Fossil Lamellibranchiate Shells of the Upper Helderberg, Hamilton, 

 Portage and Chemung groups," etc., to the number of eighty pages, issued in 

 December of that year. One hundred copies in this form were distributed. 

 In January following the printing was resumed, and sixteen additional pages 

 were printed. The pamphlet thus augmented, with a supplementary page 

 stating the fact that the descriptions of other species were in type, was dis- 

 tributed to the public. 



