EARLY PALEOZOIC BRYOZOA OF THE BALTIC PROVINCES. 197 



Although in surface characters this form 

 associated forms, its internal features are 

 its recognition easy. The chief peculiarity 

 or sections is the presence of exceedingly 

 the mesopores and comparatively few of 

 zocecia proper. In the mesopores 20 to 25 

 space of 1 mm,, while in the immature reg 



is quite similar to several 

 striking enough to make 

 seen in vertical fractures 

 numerous diaphragms in 

 these structures in the 

 diaphragms occur in the 

 ion of the zocecia only 1 



d 



Fig. 106.— Mesotrypa discoidea orientalis. a, b, and c, top, basal, and side vietvs of a zoarium, 



NATURAL size; d, TANGENTIAL SECTION, X20, "WITH THE MESOPORES SHADE! , €, A PORTION OF THE SAME, 

 X40, ILLUSTRATING THE SIMPLICITY OF STRUCTURE AND THE TENDENCY OF THE ZOCECIAL TUBES TO ASSUME 

 A HEXAGONAL OUTLINE;/, VERTICAL SECTION, X20, SHOWING PORTIONS OF TWO IMMATURE ZONES 

 BOUNDING A NARROW MATURE ZONE. JEWE LIMESTONE (Dl), BARON TOLL'S ESTATE, ESTHONIA. 



may be found in the same distance. The mature region of the zocecia 

 occasionally have as many as 4 diaphragms, which in all cases are 

 straight or but slightly curved. These are placed on an average of 

 a tube diameter apart. 



The Kussian specimens are apparently closely related to Mesotrypa 

 discoidea Ulrich, from the Nematopora bed of the lower Trenton of 

 Minnesota, with which they agree closely in size of zocecia and num- 

 ber and tabulation of the mesopores. The two differ mainly in the 



