Fauna of the Morroio Group 
97 
Remarks. In comparison with M. eugeneae, the larger size 
of corallites and corallum, as well as the approach toward 
equality in the thickness of walls and tabulae which charac- 
terizes this species, is noteworthy. M. meekana Girty from the 
Chester horizon in the Boston Mountain region is comparable to 
it in size but is probably a different species as it is said to 
have “moderately thick” walls. 
Horizon and locality. Morrow formation : near Choteau, 
Oklahoma (Stations 297 and 307). 
Michelinia subcylindrica n. sp. 
Plate I, figure 18 . 
Description. Corallum small, irregularly sub-cylindrical in 
form, with the height commonly much greater than any trans- 
verse diameter, cross-section more or less circular, the largest 
specimen 15 mm, in height, the average less than 7 or 8 mm. ; 
the base small and conical, covered with a wrinkled, concen- 
trically striated epitheca which does not extend far upon the 
sides of the colony in any of the specimens at hand ; corallites 
small, opening upon all sides of the corallum except at the 
base, polygonal, many of them hexagonal or pentagonal, in 
cross-section with slightly rounded angles, their diameter vari- 
able but the majority with a diameter between 0.5 and 1.0 mm.; 
calyces generally exceeding in depth the diameter of the corallite, 
bounded by thin walls which are ordinarily slightly thicker at 
the intersecting angles than elsewhere ; septa, tabulae, and 
mural pores as in M. eugeneae. 
Remarks. The small size of the corallites and the size and 
shape of the corallum serve to distinguish this form readily 
from the more common M. eugeneae. In a sense, the mode of 
growth of the corallum is intermediate between that of White’s 
species and the form described by Ulrich from the Ste. Genevieve 
as M. suhramosa. In comparison with the latter its corallites 
are, again, conspicuously smaller. 
Horizon and locality. Morrow formation: near Ft. Gibson, 
Oklahoma (Station 301). 
