280 BULLETIN" 11, UNITED STATES NATIONAL MUSEUM. 



from American specim.ens are shown in figure 168 for comparison 

 with the Russian specimens referred to the variety. The thin sec- 

 tions of the particular specimen illustrated in figure 167 show 

 unusually large and few acanthopores, but other sections of the same 

 example show them of the more usual size and number. 



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

 Minnesota; apparently rare in the Wassalem bed (D3) at Uxnorm, 

 Esthonia. 



Plesiotype.—C&t, No. 57383, U.S.N.M. 



Thin sections of the Russian example are in the collections of the 

 British Museum, 



Fig. 168. — Batostoma wtnchelli sPrNTJiosuM. a and 6, tangential section, x18, and a single zoce- 



CIXJM, X50, "\yiTH NUMEROUS ACANTHOPOBES. BLACK RiVER (DECOEAH) SHALES, ST. PAUL, MINNE- 

 SOTA. (After Ulrich.) 



BATOSTOMA GRANULOSTTM, new species. 

 Text fig. 169. 



Only two examples of this form are known to me, but its large 

 zooBcia and numerous large acanthopores, in addition to its internal 

 structure, form a combination of characters so different from other 

 species of Batostoma that I do not hesitate to describe it as new. 

 The example on which the description is based is a cyhndrical stem 

 8 mm. in diameter, most of which has been used in making the thin 

 sections studied. Its surface is free from monticules but granulose 

 because of the numerous acanthopores. Zocscia thick-walled, 

 irregularly polygonal with occasional mesopores. Acanthopores 

 large and numerous, eight usually surrounding a zooecium. Three 

 and one-half to four zooecia in 2 mm. Macule of larger zooecia and 

 more abundant mesopores a conspicuous feature of the surface and 

 of thin sections. 



The internal structure is that of a typical Batostoma. In the 

 vertical section figured the mature region is short and little devel- 

 oped, but the beaded mesopores and usual wall structure of the genus 

 are apparent. Tangential sections bring out the numerous large 

 acanthopores very plainly and show in addition rather few mesopores. 



