196 THE PALEONTOLOGY OF MINNESOTA. 
[Helopora. 
The dismembered zoaria of this species literally made up a thin limestone 
layer, 5 to 35 mm. thick, and about 2 meters square, which occurred in the soft 
shales near Waynesville, Ohio. It is impossible to say how many segments may 
have belonged to a single zoarium, but judging from their exceeding abundance 
here it is more than probable that the number was often very large. 
Formation and locality.—Rather a characteristic fossil of the upper beds of the Cincinnati group. 
The species is known froin localities in Ohio, Indiana and Illinois, and has been found at Stony Mountain, 
Manitoba. 
Mus. Reg, No. 8113. 
Hxnopora (?) sp. undet. 
PLATE III, FIG. 8. 
Of this form my collection contains several segments that were found associated 
with /Helopora mucronata, H. quadrata and Arthroclema armatum. After careful 
comparisons with those species, the last especially, I am obliged to regard them as 
probably belonging to an undeseribed species, which, because of the paucity of the 
material at hand, I thought best to leave unnamed. A small one of what I believe 
to be the tertiary or last set of segments of A. armatum is illustrated, beside one of 
the supposed new species, on plate III by fig. 7. This is a little shorter than usual, 
agreeing in that respect very nearly with the form under consideration, but in the 
greater strength of its longitudinal ridges and in the character and number of the 
zocecial apertures 1n a given space, it differs from the present species, while it agrees 
in these features with the ordinary form of the third set of segments of A. arma- 
tum. The segments in question are shorter than the average forms of either the 
secondary or tertiary segments of A. armatum, and taking into consideration the 
absence of a lateral socket, which should be present in segments of this diameter, if 
they belong to a species of Arthroclema, | think I am justified in maintaining, pro- 
visionally, that they belong to a species of [Zelopora, with characters, briefly, as 
follows: 
Segments short, a little over 2 mm. in length, about 0.5 mm. in diameter, eylin- 
drical, the upper extremity truncate, the lower tapering slightly but not pointed. 
Zocecia in from eight to ten longitudinal rows, but the more obvious arrangement is 
in five transverse or subspiral rows. Apertures subovate, oblique, widely separated 
longitudinally, closely arranged transversely, the last fact, together with the prom- 
inence of the posterior border, giving the stems an annulated appearance. Delicate 
ridges, which do not cross over the elevated margins of the zocecial apertures, define 
their longitudinal arrangement. 
