278 THE PALEONTOLOGY OF MINNESOTA. 
[Callopora incontroversa. 
0.2 mm. apart. In tangential sections of fully matured examples (fig. 39) the zocecia 
are decidedly angular, subequal, most of them in contact on all sides, the mesopores 
being small, very few, and sometimes restricted to certain spots where limited 
clusters may be found. 
Both the mesopores and diaphragms are less numerous than in C. multitabulata; 
the angular shape of the zoccial aperture will distinguish the species from other 
forms of the genus. I found it difficult to separate slightly abraded specimens of a 
small form of Batostoma, near B. winchelli, from those of the present species. When 
unworn the Batostoma has distinct acanthopores which are a sufficient mark, and 
when these have been removed by abrasion the student may succeed in separating 
them by measurement, the latter having eleven or twelve zocecia where C. angularis 
has nine or ten. 
Formation and locality.—Rather rare in the lower third of the Trenton shales at Minneapolis, 
Chatfield, and near Fountain, Minnesota. 
Mus. Reg. Nos. 8088, 8097. 
CALLOPORA INCONTROVERSA Ulvyich. 
PLATE XXII, FIGS. 33-36. 
Callopora incontroversa ULRICH, 1886. Fourteenth Ann. Rep. Geol. Nat. Hist. Sur. Minn., p. 96. 
Zoarium ramose ; branches smooth, subcylindrical, 4.5 to 6 or 7 mm. in diameter, 
dividing dichotomously at intervals of 12 or more mm. Zocecia with walls compar- 
atively thin ; apertures oval or subcircular, rarely polygonal ; small, inconspicuous, 
and rather irregularly distributed clusters consisting of openings slightly larger than 
the average occasionally present; about ten apertures in 38 mm. Closures occa- 
sionally preserved; central perforation larger than usual, 0.07 to 0.08 mm. in 
diameter, enclosed by a thickened rim; apparently not radially marked, Mesopores 
numerous, small, scarcely gathered into clusters, usually occupying only the spaces 
left between the contiguous rounded walls of the zocecia. 
Internal characters: Tangential sections show that the zocecia are broadly 
elliptical, rather thin-walled, and usually in contact with each other at as many 
points as their rounded form will admit. Interspaces occupied by the mesopores. 
At unequal intervals the latter may be more numerous and the zoccia a little 
larger than usual, but these clusters are never conspicuous. In vertical sections the 
tubes form a gradual but rather short curve to the surface. In their tabulation and 
general appearance the proximal ends of the zocecial tubes are so much like the true 
mesopores of the peripheral region that we cannot escape the conviction that their 
functions also were alike. From the point of origin till it has attained nearly its 
