280 THE PALEONTOLOGY OF MINNESOTA. 
[Callopora multitabulata. 
CALLOPORA MULTITABULATA Ulrich. 
TALANIEDY: SOTO, FIGS. 11, 12, 16, 17, 24, 25, 26, 30, 31. 
Monotrypella multitabulata ULRICH, 1886. Fourteenth Ann. Rep. Geol. Nat. Hist. Sur. Minn., p. 100. 
Zoarium consisting of more or less irregularly divided, subcylindrical branches, 
their diameter averaging 7 or 8 but varying between the extremes of 3 and 10 mm. 
Surface generally with more or less strongly elevated, conical or rounded monticules, 
2.5mm. from center to center. The typical form of the species occurs in the Trenton 
of Kentucxy and Tennessee, and in the upper third of the Trenton shales of Minne- 
sota. In this monticules are always present, and they are occupied by zocecia but 
little if at all larger than the average. Mesopores are exceedingly few at the 
surface, the zoccia being angular, in contact with each other, their walls thin ; 
apertures direct, with an average of eleven in3 mm. Closures preserved in a few 
specimens, ornamented as shown in fig. 26. In the underlying middle third of the 
shales and in the overlying Galena shales there is a form, rare in the first, exceed- 
ingly common in the second, that varies in having the monticules lower and even 
quite inconspicuous, the zocecia a little larger (ten in 8 mm), and the cells occupying 
the low monticules usually well distinguished by their size. Very frequently too a 
sprinkling of mesopores is detectable at the surtace, as shown in fig. 31, but it is rare 
to find them as numerous as in fig. 30. 
Internal characters: In tangential sections of the typical form the zocecia are 
regularly polygonal, generally in contact with each other on all sides, and provided 
with moderately thickened walls, in which the original boundary line between the 
zocecia is preserved as a sharp dark line. Mesopores are very few. Because of a 
lack of room no section of this form was illustrated, but a good idea of its appear- 
ance may be gathered from fig. 39 on plate XXII, and the upper third of fig. 17 on 
plate XXIII. In the Galena shales variety the appearance of tangential sections is 
generally as in the mentioned fig. 17. 
In vertical sections (pl. XXIII, fig. 24) the peripheral region is comparatively 
wider than in other species of this type. Diaphragms exceedingly abundant 
throughout the tubes, the average distance between them in the axial region being 
about equal to their diameter; in the peripheral region twelve to sixteen occur in 1 
mm. Here many of them may be slightly curved or joined to one another. An 
occasional mesopore is met with in these sections. These are very closely tabulated, 
the average number in 0.5 mm. being ten. Now and then one of the mesopores 
may widen and assume the characters of a true zocecium. 
In the central part of transverse sections the size of the tubes and the appear- 
ance in general is intermediate between figs, 20 and 21 of plate XXIII. 
