BRYOZOA. ie 
Callopora undulata.) 
mature size, the tube is crossed by from ten to twenty or more closely and regularly 
arranged diaphragms. After this the diaphragms are much farther apart, and in 
many tubes may be wanting entirely until they enter the peripheral region when 
they once more come close together. 
This species is distinguished from C. undulata by its slightly ited size, smooth 
surface, and slight differences in the tabulation of the tubes. In tangential sections 
the zocecia of that species are less rounded. C. goodhuensis and C. ampla have fewer 
mesopores and more abundant diaphragms. 
Formation and locality—Rather rare in the lower third of the Trenton shales at Minneapolis, 
St. Paul and Preston, Minnesota. 
Mus. Reg. No. 7653. 
CaLLopora uNDULATA Ulrich. 
PLATE XXII, FIGS. 24-31. 
Callopora undulata ULricH, 1886. Fourteenth Ann. Rep. Geol. Nat. Hist. Sur. Minn., p. 95. 
Zoarium ramose, branches slender, averaging about 2.5 or 3.0 mm. in diameter, 
dividing dichotomously at intervals of 10 mm. or more. Surface with rather large, 
rounded monticules, that usually coalesce laterally, forming transverse ridges, or 
more or less complete annulations, five in ten mm. In some fragments and portions 
of others the monticules are separate, while in a few they are nearly obsolete. Zocecia 
with moderately thin walls, subangular or ovate apertures, of nearly equal size over 
all portions of the surface ; ten or eleven in 83mm. Mesopores comparatively few, 
small, not readily distinguished externally, their mouths usually closed. Zocecial 
covers not observed. 
Internal characters: These are sufficiently shown in the illustrations, and, as 
‘they are also very similar to those of the preceding species, I shall only point out 
the differences. The walls in tangential sections are thicker than in C. incontroversa, 
the divisional line between adjoiuing zocecia more distinct, and the mesopores less 
numerous. 
C. angularis has a smooth surface, fewer mesopores, and more crowded dia- 
phragms. C. ampla is distinguished in like manner, and C. incontroversa, externally, 
by its smooth surface and more rounded zocecial apertures. 
Formation and locality.—Not uncommon in the upper part of the middle third of the Trenton shales 
at Minneapolis and St. Paul, Minnesota. 
Mus. Reg. No. 8113. 
