EAELY PALEOZOIC BEYOZOA OF THE BALTIC PROVINCES. 



231 



The average zooecium is 0.35 mm. in diameter, but the large aper- 

 tures of those in the maculae attain a size half again as great. Count- 

 ing the intervening mesopores, three to four zooecia occur in 2 mm. 

 The minute structure of the walls in both sections has been described 

 under the diagnosis of the genus. The glassy aspect of the material 

 composing the zoarium and the rough fracture of the tubes has also 





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Fig. 128.— Dianulites fastiglvtus. a, vertical sectiok, X9, with dlvpheagms in the mesopoees 



only; 6, PART OF THE SAME SECTION, X20, SHOWING THE WALL STRUCTURE; C, TANGENTLVL SECTION, X20, 

 WITH THE ZOCECIA SHADED TO DISTINGUISH THEM FROM THE MESOPOEES; d, ANOTHER PART OF THE SAME 

 SECTION, X40, ILLUSTRATING THE MICROSCOPIC STRUCTURE OF THE WALLS. ECHINOSPHEEITES LIME- 

 STONE (01), DUBOVIKI, ON THE WOLCHOW RiVER, GOVERNMENT OF St. PETERSBURG. 



been noted and is particularly evident in D.fastigiaius. The walls of 

 both zooecia and mesopores are gently undulating. 



Dybowski's figures of the internal structure (pi. 2, figs. 1-3), 

 although probably derived in part from thin sections of the species, 

 are misleading in that he considered all of the subequal apertures to 

 be zooecia. The tabulation shown in figure 3 is undoubtedly taken 

 from a section of another species, but the minute structure of the 

 walls, as indicated in figure 1, is correct. 



Compared with other members of the genus, the turbinate shape of 

 the zoarium and the numerous large mesopores are alone sufficient to 



