EAELY PALEOZOIC BEYOZOA OF THE BALTIC PEOVINCES. 93 



celluliferous surface. The specimen shown on plate 6, figure 6, is 

 40 mm. in its greatest width, and does not exceed 2 mm. in thickness. 

 By the superposition of several layers of zooecia, the thickness of a 

 zoarium may reach as much as 6 or 8 mm. The celluhferous face 

 bears indistinct maculas of zooecia slightly larger than the average at 

 regular intervals of about 4 mm., but such areas are best determined 

 by the radiate arrangement of the zooecia about them. The maculae 

 sometimes occupy the central portion of low, domehke elevations, 

 but a plain, smooth, celluliferous surface is of more frequent occur- 

 rence. Zooecia large, 4 to 5 in 2 mm., with thin walls and direct 

 subrhomboidal apertures. Mesopores few, with an occasional one 

 scattered among the zooecia, but most frequently restricted entirely 

 to the maculse. Lunaria usually a well marked, erect crescent, situ- 

 ated in the acute angle of the zooecium, and directed away from the 

 maculae. 



The essential features of the internal structure are believed to be 

 shown in the accompanying figures, so that it will only be necessary 

 to call attention to a few points. The vertical section is exceptionally 

 like that shown in explanate species of many other ceramoporoid 

 bryozoans, with the exception that the cell walls are pierced by 

 distinct connecting pores which give a beaded aspect to the walls. 

 None of the various vertical sections studied has shown a trace of 

 diaphragms, so that these are apparently wanting entirely. The 

 large connecting pores penetrating the zooecial walls are plainly 

 visible in both vertical and tangential sections, but especially in the 

 former. Their appearance in specimens with clay-filled zooecia is 

 shown in figures 29 c to e, the pores themselves being occupied by 

 solid, earthy material and thus sharply marked ofT from the calca- 

 reous wall of the zocecium itself. When the zooecial tubes have been 

 filled with calcite, the pore is naturally not so distinctly visible, 

 although it can still be discerned without difficulty. In figure 29 c 

 the zooecial walls are cut across directly so that their edges only are 

 visible, but in figures 29 d and e, portions of the same section, the 

 flat side of a wall has been included in the section. The latter figures, 

 therefore, show transverse views of the pores in the shaded areas 

 and vertical sections of them in the remaining portions. 



The occurrence of four to six tubules in each lunarium is the most 

 striking feature of tangential sections. Their appearance and the 

 general shape, size and position of the lunarium, are shown in figure 

 29 a. The rhomboidal shape of the zooecia so characteristic of sur- 

 face views is not as well marked in thin sections, especially where 

 mesopores are introduced. The aspect of part of a macula and its 

 surrounding zooecia is illustrated in figure 29 5. In both figures, the 

 disconnected walls showing here and there are indicative of the con- 

 necting pores so well shown in the vertical sections. 



