262 THE PALEONTOLOGY OF MINNESOTA. 
{Mesotrypa (?) rotunda. 
Mrsorrypa (?) ROTUNDA, ”. Sp. 
= 
FH Tas fone 
= =e: 
ae, = 
Rae: So 
a ERS 
Fig. 17. Mesotrypa rotunda Ulrich, upper beds of the Galena shales, Hader, Goodhue county, Min- 
nesota. Collection of E.O. Ulrich. 1, tangential section showing arrangement of cells about one of the 
clusters. The latter embraces several young zoccia. 2, another portion of same section, with half of a 
cluster shown above. 3, vertical section passing through a cluster like the one represented in 1, and 
showing at center of figure several mesopores that have enlarged and assumed the tabulation of zooscial 
tubes. 4, another portion of same section showing a partial break in the continuity of the tubes, and 
consequent irregularities in their tabulation. All x 18. 
Zoarium a small hemispheric mass, 10 mm. in diameter, 6 mm. high, and 4 mm. 
thick at the middle, the under surface being strongly concave and wrinkled concen- 
trically. Upper surface without monticules, but exhibiting fairly distinct clusters 
of large cells, rendered in many cases more so by aggregations of mesopores. Zoce- 
cial apertures rounded, about eleven of the average size in 3 mm. Mesopores 
abundant, but seeming never to separate the zocecia completely. Acanthopores 
wanting. 
Internal structure as shown in the accompanying figures. 
This form is distinguished from the other species of the genus in having all the 
diaphragms essentially horizontal. This fact casts some doubt upon the propriety of 
placing the species under Mesotrypa, and the uncertainty of the reference is empha- 
sized by undoubted relations with species now classed as Diplotrypa (e. g. D. millert 
Ulrich, and D.? dubia Ulrich), having a decided leaning toward Callopora. 
Formation and locality.—Lower beds of the Galena limestone at Hader, Goodhue county, Minnesota. 
