542 DR. A. W. ROWE ON THE GENUS MICRASTER. [Aug. 1 899, 



The distribution of species and varieties may be diagrammatically 

 represented thus : — 



HlGH-ZOJTAL 



Skkies. 



Zone of 

 M. cor-anguinum. 



Lower third of this 

 zone. 



Zone of 

 M. cor-testudinarium 



Zone of HolasUr 

 planus. 



Zone of Terebratulin 

 gracilis. 



2^ote.—Th% above diagram does not show, as it should do, that M. LesJm occurs 

 in the zone of Ehynchonella Cuvieri, but allusion is made to the fact on the 

 following page. 



