BRYOZOA. 277 



Callopora angularis.l 



s true the zooecial 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 zooacial 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 Batostomce 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 Callopora; 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, n. sp. 



PLATE XXII, FIGS. 37-41. 



Zoarium small or of medium size ; branches 3 to 5 mm. in diameter. Zoo3cial 

 apertures angular, subequal, about nine and a half in 3 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 



