(tKABAU 



— Faunas of the Hamilton Group. 



319 



The twenty species marked (f) occur for the first time in this 

 region. Those marked (*) pass upwards into the lower Moscow shale 

 Nineteen species therefore are entirely restricted to the Encrinal limestone. 

 In addition to these the following are characteristic of this rock : 



Phacops rami, Modiomorpha concentrica, Rhipidomella Vanuxemi, 

 Stropheodonta nacrea, Spirifer granulosus, S. macronotus, Cryptonella plani- 

 rostra and Tropidoleptus carinatus. 



D. The fauna of the Lower Moscow shale or the Spirifer consobrinus fauna. 



This fauna is characterized by the abundant development of S. consobrin us 

 D'Orb., which has entirely replaced 8. mucronatus. This latter form is 

 extremely rare, only a few poorly preserved specimens having been obtained. 

 The fauna occupies the lower four or five feet of the shale, after which fossils 

 become rare. S. consobritius is not found outside of this horizon, but 

 characterizes it wherever examined. The fauna admits of subdivision into 

 several groups as follows; 



a. The lower foot and three-quarters of shale, poorly laminated and 

 weathering into a tenacious clay, contains ; 



Crustacea ; 



1 Phacops ran a. rc 



2 Cryplneus Boothi. r 



Lamellibranchiata : 



55 Pala?oneilo tenuistriata. R 



56 P. fecunda. r 



57 P. muta. rc 



66 Cypricardinia indenta. R 



Rrachiopoda ; 



79 Pholidops Hamiltonia3. c 



91 Stropheodonta perplana. c 



97 Chonetes deflecta. rc 



99 C. scitula. r 



100 C.lepida. r 



108 Spirifer consobrinus. rc 



116 Amboccelia umbonata. C 



121 Athyris spiriferoides. rc 



