Orb. hilli 
5 large and 3 young calices . The calices are not so prominent, 
nor so divergent as in the type. 
There are between 50 and 70 septa, usually with about 12 
that are distinctly thicker than the other, the cycles are fair- 
ly well indicated. The first and second cycles are nearly 
equal in thickness, the tertiaries are thinner, the quaternaries 
and quinaries still smaller. The primaries and secondaries 
reach the columella, the tertiaries frequently do, and where 
quinaries are present the quaternaries may. The Esepjra are 
crowded, their upper margins curved directly from the costae 
the columella thus obscuring the upper edge of the theca. 
The costal portions of the septa are the thickest, the decrease 
in thickness toward the corallite axis is gradual. 
Axial fossa slightly sunken but shallow. Columella 
relatively smaller, occupying about l/4 the diameter of the 
corallite cavity; upper surface papillose. 
