24 



Report of the State Geologist. 



both measurements of thickness, and identification of species of fossils have 

 been made with care, and while the conclusions are not in complete harmony 

 with already expressed opinions, they doubtless afford a more orecise knowl- 

 edge of the formations considered. 



Palaeontology. 

 Note on the Discovery of a Sessile Conularia. 



By R. Ruedkmaxx. 



This important paper by Dr. Rnedemann, who contributed to the report 

 of last year an interesting memoir on the Graptolites, is based upon the study 

 of some obscure organisms found in the Utica slate at Dolgeville, N. Y. 

 Portions of this paper have already been published during the past year in 

 the American Geologist, and they make so significant a contribution to our 

 knowledge of the fossils of this State that, with the author's consent, these 

 portions are here reproduced with their accompanying plates. To these are 

 added further observations and illustrations. As a result of this study much 

 light is thrown upon the nature and mode of development of this wide-spread 

 but little understood organism, Conularia, in regard to whose taxonomic 

 position there has been a widely diverse expression of opinion. 



A Discussion of Streptelasma and Allied Genera of Rugose Corals. 



By James Hall. 



The genus Streptelasma has never yet been clearly defined, and thus the 

 nomenclature assigned to it has been one of general and conventional use. 

 The entire group of American species which have been referred to this genus 

 are here brought together and their structural characteristics carefully 

 analyzed. It has been found that the term Streptehoiuut must be carefully 

 restricted to Eorms like the 8. comiculum, Hall, of the Trenton fauna. Devia- 

 tions Prom this type of generic structure are here recognized under distinct 

 designations: Thus the 8. mammifer, Hall, of the Upper Helderberg lime- 

 stone, 8. caliculum, Hall, of the Niagara group, and 8. rectum, Hall, of the 

 Hamilton shale, ;ire each made the type of n distinct genus. A new form 



