206 NEW YORK STATE MUSEUM 



*Hexameroceras chadwicki Ruedemann rr 



Worm-borings cc 



Leperditia scalaris Jones cc 



L. sp. r 



Emmelzoe decora Clarke r 

 *Ceratiocaris salina Ruedemann cc 



C. cf. praecedens Clarke rr 



Eurypterus pittsfordensis Sarle cc 



Mixopterus multispinosus {Clarke i^ Ruedemann) 

 *Hughmilleria phelpsae Ruedemann rr 

 *Pterygotus vernonensis Ruedemann rr 



The complete list of the Pittsford shale fauna (see Clarke 1901, 

 Sarle 1901, Ruedemann 19 16) is: 



Lingula semina Ruedemann cc 



Pterinea poststriata Ruedemann cc 



Hexameroceras cf. chadwicki Ruedemann rr 



Orthoceras sp. rr 



Leperditia scalaris Jones cc 



Emmelzoe decora Clarke r 



Pseudoniscus roosevelti Clarke rr 



Ceratiocaris praecedens Clarke rr 



Eurypterus pittsfordensis Sarle c 



Mixopterus multispinosus {Clarke i^ Ruedemann) rr 



Hughmilleria socialis Sarle c 



H. socialis var. robusta Sarle rr 



Pterygotus monroensis Sarle rr 



A comparison of these faunules^ brings out the fact that they are 

 alike in their general aspect and composition. Disregarding the 

 species that are very rare in either of the two formations and therefore 

 might be present in the other, but have failed of observation, the 

 principal difference between the two faunules consists in the common 

 occurrence of Hughmilleria socialis in the Pittsford 

 fauna and its absence in the Vernon fauna where it is replaced by the 

 rare H. phelpsae ; and further in the abundance of the minute 

 Ceratiocaris salina in the Vernon shale, which as yet 

 has not been observed in the Pittsford shale. One might therefore 

 well designate the Pittsford shale as the horizon of H u g h m i 1- 



^The new forms in the Vernon shale are marked with an asterisk. The 

 designations of frequency of occurrence (cc, c, r, rr) are only relative. 



