EAELY PALEOZOIC BEYOZOA OF THE BALTIC PROVINCES. 333 



monticules are separate, while in a few they are nearly obsolete. Zooecia with moder- 

 ately thin walls, subangular or ovate apertures, of nearly equal size over all portions 

 of the surface; 10 or 11 in 3 mm. Mesopores comparatively few, small, not readily 

 distinguished externally, their mouths usually closed. Zooecial covers not observed. 



Occurrence. — Common in the Black River (Decorah) shales at 

 Minneapolis and St. Paul, Minnesota, and in the Wassalem beds (D3) 

 atUxnorm, Esthonia (Cat. No. 57469, U.S.N.M.). 



British Museum, specimen and thin section from Uxnorm. 



Fig. 209.— Hallopora tolu. a, small feagmekt, natural size; 6, tangential section, X20, show- 

 ing LARGE, TmN-WALLED-ZOCECIA "WITH NUMEROUS MESOPORES; C AND d, TWO PORTIONS OF A VERTICAL 

 SECTION, X20, EXHIBITING TABULATION. KUCKEES SHALE (02), REVAL, ESTHONIA, AND JEWE LIME- 

 STONE (Dl), Bakon Toll's estate. 



HALLOPORA TOLLI, new species. 



Text fig. 209. 



This well marked species forms smooth, cylindrical branches 6 to 8 

 mm. in diameter, very much like H. wesenbergiana, but differing con- 

 spicuously in having much larger zooecia. Internally the two are 

 quite distinct, as a glance at the figures, especially of vertical sec- 

 tions, will show. In tangential section, H. tolli exhibits its polygonal 

 to rounded, thin-walled zooecia, four in 2 mm., with a fair number of 

 small, angular mesopores. In the maculae the mesopores are occa- 

 sionally numerous enough to isolate the zooecia, but elsewhere they 

 are seldom so abundant. 



