86 NEW YORK STATE MUSEUM 



Anastrophia, the upper Siluric representative of the earlier 

 Parastro p h i a, is represented .in the Helderbergian, but it was also 

 present in the calcareous Oriskany. 



Sieberella attains its highest development in the Siluric and 

 its species (S . galeata and S. pseudogaleata) are of frequent 

 occurrence in the Helderbergian. The type, however, does not end here, 

 but is continued upward into the Mesodevonic, even the species S . 

 galeata being commonly identified from these horizons by European 

 writers. 



Bryozoans. But few Siluric affinities are expressed in this group. 

 Rhinidictya presents its latest species. Diamesopora and C a 1 - 

 1 o p o r a range from lower Siluric upward into the Onondaga limestone. 



Crinoids. None of the crinoids are of distinctively Siluric char- 

 acter. 



Cyst ids. The presence of Anomalocystites (though this genus 

 occurs in the Oriskany), Lepadocrinus, Sphaerocystites, is 

 suggestive of waning Siluric traits. The cystids are not absent from 

 succeeding faunas, but are of rare occurrence. 



Corals. Duncanella r u d i s of the Helderbergian is anticipated 

 by D . borealis of the Niagaran and succeeded by D . truncata of 

 the Onondaga. 



E n t e r o 1 a s m a (E . strictum) is the last representative of a 

 genus which makes its other appearance in the Niagaran. 



Graptolites. Girty has described Monograptus beecheri from 

 the Helderbergian. Before this interesting discovery we had no knowl- 

 edge of the continuation of the rhabdophorous graptolites beyond 

 the Niagaran fauna except in the case of Dictyonema, which is not 

 uncommon in the Mesodevonic. There are several structural features, 

 indicated by Mr Girty's description and figure, which indicate that M. 

 beecheri Avill not prove a representative of the Monograptus type 

 of the Siluric. Freeh has expressed the view that such forms are 

 probably Retiolites. 



Negative elements 



The absence of the Devonic types, Cryphaous and G o n i a t i t e s, 

 is noteworthy. 



