BRYOZOA. 433 



Zoopcial tubes for a short distance after their origin rather 

 closely tabulated, afterwards the diaphragms become about two 

 tube diameters or less apart. Mesopores moderately abundant, 

 with rather close-set diaphragms. Acanthopores very small. 



In the oval form of the cells, the numerous mesopores, the 

 frequent closure of the cell apertures by perforated opercular 

 structures, this species is remarkably like Callopora sigillaroides 

 Nich., but its internal structure is altogether different. Intern- 

 ally it can scarcely be distinguished from B. trentonensis Nich., 

 from the Trenton limestone of Ontario, but the smaller size of 

 this species, and its rather more oval apertures and different 

 horizon discriminate the form from that. 



Position and locality: Cincinnati group, Savanna, 111., and at 

 a number of localities in Ohio and Indiana, where the upper 

 beds of this formation are exposed. 



BATOSTOMELLA OBLIQUA Ulrich. 



PL XLVL fig. 2-2c. 



Zoarium dendroidal, consisting of dichotomously and other- 

 wise branching stems, of an average thickness of six mm. Sur- 

 face marked with low rounded tubercles composed of larger 

 sized cell apertures; centers of clusters 2.5 mm. apart. Zooecial 

 tubes slightly tortuous, opening very obliquely upon the sur- 

 face, their walls thin and somewhat flexuous in the axial re- 

 gion, rather thick in the cortical zone. Both tangential and 

 vertical sections show that the central portion of the wall is 

 granular. Apertures angular, eldngated, owing to their obli- 

 quity, those occupying the monticules especially so, about seven 

 in two mm. measuring lengthwise. Mesopores few or wanting. 

 Two or three diaphragms developed just before the tubes enter 

 the peripheral region. A few faint and small acanthopores ap- 

 pear to be present in tangential sections; not observed on the 

 surface. 



The great obliquity of the tubes, the absence, more or less 



complete, of mesopores, and the angular elongated apertures 



are the most distinctive characters of this form. The granular 



structure of the central portion of the walls is the chief ground 



54 



