96 
Kirtley F. Mather 
tudinal striations on the inner walls of the calyx but not easily 
discernible in cross-sections ; tabulae numerous, very thin, 
irregularly spaced, more commonly convex upward but in some 
instances plane or concave, not all completely crossing the 
corallite from wall to wall, but some arching from the central 
portion of the preceding tabula to the wall of the corallite; 
mural pores with a diameter about one-third as great as the 
width of the walls, not numerous, irregularly scattered. 
Remarks. There can be no doubt, so far as a study of de- 
scriptions and figures indicates, that the forms thus described 
are conspecific with those to which this name was first given 
by White. The arrangement of tabulae and mural pores makes 
quite clear the correctness of the generic reference. 
Horizon and locality. Brentwood limestone: near Fayette- 
ville (Stations 135, 147, and 152), and Brentwood (Station 145), 
Arkansas; Sawney Hollow, Oklahoma (Station 210). Kessler 
limestone: near Brentwood, Arkansas (Station 144). Morrow 
formation: near Ft. Gibson (Stations 296 and 301), Choteau 
(Stations 298 and 302), Hulbert (Station 299), and Gore (Sta- 
tion 305), Oklahoma. 
Michelinia exilimura n. sp. 
Plate II, figures 2, 2a. 
Description. Corallum a large, irregularly expanding len- 
ticular mass which may attain a diameter of at least 125 mm. ; 
corallites polygonal, many of them hexagonal or pentagonal in 
cross-section, variable in size, but commonly with a diameter 
between 3 and 6 mm. ; calyces, basal attachment, and epitheca 
not preserved in either of the two specimens at hand; as dis- 
played in sections the corallite walls are very thin, scarcely half 
as thick as those of M. eugeneae, the tabulae are very numerous, 
from 5 to 7 occurring in the space of one diameter in the axial 
region, quite variable in curvature with probably a slight pre- 
ponderance of those which are convex upward, nearly as thick 
as the inter-corallite walls and in many cases directed at acute 
angles with the walls, thus intersecting each other at diverse 
angles; mural pores are small, irregularly distributed, and not 
very abundant. 
