EARLY PALEOZOIC BEYOZOA OP THE BALTIC PROVINCES. 275 



In the above description Ulrich has embodied all of the essential 

 features of the species. The Eussian examples referred here are so 

 similar externally and internally that there can be little doubt of the 

 correctness of their reference to Batostoma fertile. 



>-. / 



Fig. 163. — Batostoma fertile, a and 6, a large and a small specimen, natural size; c, surface 



OF THE LARGER SPECIMEN, X9; d, TANGENTIAL SECTION OF THE SAME EXAMPLE, X18; €, VERTICAL SEC- 

 TION, NATURAL SIZE, AND A PORTION, X18. BLACK RiVER (DECORAH) SHALES, MINNEAPOLIS, MINNE- 

 SOTA. (After Ulrich.) 



Occurrence. — Common in the Stictoporella bed of the Black River 

 (Decorah) shales of Minnesota; rare in the Echinospherites lime- 

 stone (CI) near Reval, Esthonia (Cat. No. 57378, U.S.N.M.). 



American specimens of the species are in the collections of the British 

 Museum. 



BATOSTOMA FERTILE CIRCULARE Ulrich. 



Text fig. 164. 



Batostoma fertile var. circulare Ulrich, Geol. and Nat. Hist. Surv. Minnesota, vol. 

 3, pt. 1, 1893, p. 291, pi. 25, figs. 8, 9; Zittel's Textbook of Paleontology 

 (Eng. ed.), 1896, p. 275, fig. 459 B. 



The distinctive feature of this variety is pointed out in the above 

 description, and illustrated in the accompanying figure, although 

 often the peristomes are thicker and more distinctly separated from 

 each other than is shown in the figure. Both species and variety 

 are found associated in American strata and likewise in the Russian. 



