194 THE PALEONTOLOGY OF MINNESOTA. 



[Eel opora 



This is the only species of the genus known to me having quadrate segments 

 and only four rows of zocecia. 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 zooecial 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 zocBcial apertures, it is evident that 

 the species does not belong to that genus. 



Formation and ZocaKfy.— Comparatively rare in washings of the Galena shales, near Cannon Falls, 

 Minnesota. 



Helopora elegans, n. sp. 



Fig. 11, Helopora- elegans Uleich, 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 0.3 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 striae 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 zooecial 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. 

 H. 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 Eichmond 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. 



