Orb. hi Hi 
Locality • Island of Antigua, West Indies; R. T. Hill, 
Collector* 
Geologic horizon : Upper Oligocene. 
Type : Museum of Comparative Zoology. 
Remarks : This is one of the most sharply defined 
species of the American Orb Icellae . It differs from the 0. 
crasBolamellata group by not having wedge shape costae and. septa, 
from the 0. cavernosa g roup by having primary and secondar:/ 
septa strikingly thicker than those of the higher cycles 
