422 



Forty-second Report on the State Museum. 



Polypi. 



Cksetetes undulatus, cnf. Ch. tabulatus, U. H. 



Emmonsia? cnf. hemisphcerica, analog. Fav. Emmonsi, U. H. 



The value of the foregoing comparisons is much obscured in citing 

 them with this brevity, for every palaeontologist knows how easy it is 

 to point out similarities in species even of widely different age. Of 

 much additional importance are Kayser's comparative observations on 

 the Hercynian and American faunas (pp. 274-279). 



" The Niagara limestone has long been the recognized equivalent 

 of the Gotland limestone, and the Bohemian etage E." 



" The water limestones overlying the Salt group contain Pterygotus 

 and other great Crustacea and on this account were regarded 

 by Murchison as the equivalent of the Tilestones, the cap-formation 

 of the English Silurian." (Quart. Jour., 1855, p. 24.) 



" In the overlying Lower Helderberg group we encounter Trilobites of 

 the genera Lichas, Phacops, Homalonotus, Cheirurus [?], Calymene [?], 

 Acidaspis, Proetus, Encrinurus [?] and Dalmanites. With the excep- 

 tion of Encrinurus all are genera with which we are familiar in the 

 Bohemian and Hartz Hercynian, and as for the Dalmanites they all 

 belong to the group of D. pleuroptyx, a form most closely related to 

 the species so important in the European Hercynian, D. Hausmanni. 

 Genuine Silurian types, like Ampyx, Illsenus, Asaphus, etc., fail. The 

 Cephalopods afford no notable features. Ascoceras, a genus still extant 

 in the Niagara, is here extinct. Among the Brachiopods there are still 

 many points of attachment to the Niagara, but no longer any genuine 

 Silurian types. On the other hand, besides the first of the Terebra- 

 tulidse (Rensselseria, which reaches a culmination in the Oriskany 

 sandstone) are long-winged Spirifers (perlamellosus, cyclopterus, 

 concinnus). A most noteworthy feature among the Gastropods is 

 the enormous development of the Capulidse (yet but rarely repre- 

 sented in the Niagara), Platystoma, Platyceras, Strophostylus, etc., 

 as the predominance of Capulids forms one of the chief characters or 

 peculiarities of the European Hercynian fauna, and this common 

 character is rendered all the more forcible as we find among the 

 American Capulids, a number of forms which show a similarity to 

 those of the Hartz. The occurrence of numerous Pterineas and 

 entire layers filled with Tentaculites are features which certainly 

 point to the Devonian rather than to Silurian. The same is true of 

 the genus Michelina among the Corals, and Polypora among the 

 Bryozoa, while on the other hand, the comparatively abundant Cysti- 

 deans remind one of the Silurian. And, finally, it is to be noticed that 

 a very considerable number of species both of Brachiopods and Gas- 



