BRYOZOA. 277 
Callopora angularis.] 
s true the zocecial tubes of the latter are larger than is usual in Callopora, yet even 
in this respect the genera are brought together by C. magnopora Foerste, of the Clin- 
ton rocks of Ohio. In the remaining features the agreement is marked, both having 
more or less numerous mesopores and no acanthopores, while the tabulation of the 
tubes is essentially the same in the two genera, the proximal ends of the tubes being 
crossed by numerous diaphragms. 
Batostoma, another genus of that family, also agrees closely with Callopora, the 
principal differences being the abundant presence of acanthopores, an irregularity 
in the tabulation and walls of the axial portion of the tubes, and the more ring-like 
character of the peripheral part of the zocecial investment in Batostoma. These 
differences, however, are less obvious when we compare some of the earlier species 
referred to the two genera. Take, for instance, B. decipiens and B. winchelli, and C. 
angularis, of the Birdseye shales of Minnesota. In these species the mesopores are 
very few, the tabulation of the tubes alike in essential respects, and the axial region 
in transverse sections made up of large and small tubes. As differences we note that 
the Batostome have the walls more irregular in the axial region and thicker in the 
peripheral, and possess acanthopores, which are wanting in the Callopora. 
Simple forms of the genus like C. angularis and C. multitabulata also remind one, 
especially in tangential sections, of Monotrypella, but it is more than doubtful that 
this resemblance indicates relationship. In any event I am now satisfied that I was 
in error in placing C. multitabulata with Monotrypella. This species differs from ordin- 
ary Callopore only in having fewer mesopores and more diaphragms, both points of 
slight importance. True Monotrypella is distinguished at once from Callopora by the 
subequal size of the tubes in the axial region of transverse sections. 
CALLOPORA ANGULARIS, 2. Sp. 
PLATE XNXII, FIGS. 37-41. 
Zoarium small or of medium size; branches 3 to 5 mm. in diameter. Zocecial 
apertures angular, subequal, about nine and a half in3 mm, Mesopores very few, 
occurring chiefly in small clusters. Walls rather thin, ridge-shaped. 
Internal characters: Vertical sections show numerous diaphragms, whose distri- 
bution in the outer third of the section is shown in fig. 38 better than can be 
described. In the central third the proximal ends of the tubes increase very slowly 
in size. Here the diaphragms are also closer together than higher up in the tube. 
The axial region therefore appears as made up of two sets of tubes, one large with 
diaphragms averaging 0.25 mm. apart, the other small with diaphragms from 0.1 to 
