194 THE PALEONTOLOGY OF MINNESOTA. 
{Hel opora 
This is the only species of the genus known to me having quadrate segments 
and only four rows of zowcia. Fragments look a little like small pieces of Nemato- 
pora ovalis, an associated species, but are readily enough distinguished by their 
sharper angles, and the relatively much greater elevation of the posterior margin of 
their zocecial apertures. 
The exceeding delicacy of the segments, and their structure in general, gives 
them very much the appearance of species of Arthrostylus. But as all of the four 
faces are occupied uniformily each by a row of zoccial apertures, it is evident that 
the species does not belong to that genus. 
Formation and locality.—Comparatively rare in washings of the Galena shales, near Cannon Falls, 
Minnesota. 
HELOPORA ELEGANS, 1. sp. 
Fig. 11, Helopora elegans ULRicH, Cincinnati group, Blanchester, Ohio, A segment of this species 
of the natural size and x 18. 
Segments small, subcylindrical, obtusely hexagonal in cross-sections, about 3.0 
mm. long and 0.38 mm. in diameter; upper extremity truncate, the lower rounded and 
tapering slightly. Zocecia in six longitudinal ranges, their apertures narrow-ellipti- 
cal, slightly depressed in front, their length apart, arranged alternately in adjoining 
rows. Entire surface beautifully grano-striate,-the striz flexuous, forming con- 
nected peristomes, with a short row of granules between the ends of the apertures 
and a continuous row at each angle of the segment. The latter winds itself between 
the zocecial apertures so as to arrange them into longitudinal series, with seven or 
eight in the length of the segment. 
Of all the species known to me H. alternata seems to be the nearest to this. 
The differences between them are however too obvious to require pointing out. 
IT. harrisi occurs in the same beds, but its segments are longer and more slender, its 
zocecia smaller, and the surface marking quite different. 
Formation and locality.—The types are from the upper beds of the Cincinnati group, at Blanchester, 
Ohio, but the species has been noticed at other localities in Ohio, and at Richmond and Versailles 
in Indiana. I have also noticed similar segments in equivalent rocks at localities in Illinois, so that the 
species may be expected to occur in these beds at localities in southern Minnesota. 
