EAELY PALEOZOIC BRYOZOA OF THE BALTIC PROVINCES. 281 



Altogether the numerous large acanthopores will distinguish this from 

 other species of the genus which have equally large zooecia. A very 

 similar, undescribed, or possibly the same species, is present in the 

 Black River rocks of America. 



Occurrence. — Rare in the Jewe limestone (Dl), Baron Toll's 

 estate, near Jewe, Esthonia, and in the Itfer limestone (C3), north of 

 Wesenberg, Esthonia. 



Holotype.— Cat. No. 57384, U.S.N.M. 



British Museum, thin sections of the type-specimen, and a speci- 

 men from the Itfer limestone, north of Wesenberg. 



Fig. 169.,— Batostoma geaitoxostim:. a, the sectioned ttpe-specimen, natural size; 6, tangential 



SECTION OF MATUEE ZONE, X20, SHOWING NUMEKOUS GRANULE-LIKE ACANTHOPORES; C, VERTICAL SEC- 

 tion, x20, with the mature zone only a little developed. jewe limestone (dl), baron 

 Toll's estate, Esthonia. 



Genus HEMIPHRAGMA UlHch. 



Batostoma (part) Ulrich, Geol. Surv. Illinois, vol. 8, 1890, p. 379. 



Hemiphragma Ulrich, Geol. and Nat. Hist. Sm-v. Minnesota, vol. 3, pt. 1, 1893, 

 p. 299; Zittel's Textbook of Paleontology (Eng. ed.), 1896, p. 275.— Simpson, 

 Fourteen th Ann. Rep. State Geologist of New York for the year 1894, 1897, 

 p. 592.— NicKLEs and Bassler, Bull. 173, U. S. Geol. Surv., 1900, p. 35. 



The genus HemipJiragma was established by Ulrich to include four 

 American species apparently closely related to Batostoma, but differ- 

 ing in having incomplete instead of complete diaphragms in their 

 m.ature region. A ramose form, Batostoma irrasum Ulrich, occurring 

 in the Middle Ordovician strata of Minnesota and Iowa, was selected 

 as the genotype, and its style of growth was regarded as a generic 

 characteristic. Since that time a fifth ramose species, Monticulipora 

 wTiitfieldi James, from the Eden division of the Cincinnatian rocks, 



