EAELY PALEOZOIC BRYOZOA OF THE BALTIC PROVINCES. 235 



identification. Variety Tiexaporites, from its description and illus- 

 trations, and from numerous specimens before me, refers, so far as 

 my knowledge goes, to only one bryozoan — a form of Dianulites 

 petropolitana in wliicli the maculse with their surrounding zooecia 

 form polygonal areas bounded by thin crests or walls of mesopores 

 (see pi. 10, figs. 10, 11). Such an occurrence is not restricted to 

 this genus, since the same polygonal areas are formed on specimens 



Fig. 131.— Dianulites peteopoutana. a and 6, side and basal views of the vaelett in the Wesen- 



BEKG limestone; C and d, tangential section, X20, AND WALL STKUCTUEE OF SAME MUCH ENLAEGED, 

 SHOWING IDENTITY WITH THE TYPICAL FOEM OF THE SPECIES; C AND/, YEETICAL SECTION, X9 AND X20, 

 WITH FEWEE DXAPHEAGMS THAN USUAL. WESENBEEG LIMESTONE (E), WESENBEEG, ESTHONIA. 



of Stellipora and Constellaria, but the present species is the only 

 Dianulites in which they have been observed. As shown in plate 10, 

 figure 11, the same specimen may present the characters of both the 

 species and the so-called variety. The latter is, therefore, placed in 

 synonymy, as is also the name Hexaporites, which, moreover, was 

 never described as a generic name. 



On account of the complicated history and rather curious varia- 

 tion of Dianulites petropolitana, the species has been illustrated in 

 some detail. Comparison of figure 130 with figure 132 shows essen- 

 92602°— Bull. 77—11 17 



