240 BULLETIN 11, UNITED STATES NATIONAL MUSEUM. 



The nodulated surface of the zoarium and conspicuous granulated 

 zooecial walls are the most obvious characters which may be employed 

 in distinguishing this species. The similarity in internal structure 

 to D. petropolitana has been mentioned, and it is possible that larger 

 collections will prove the present species to be more closely related 

 than now recognized. 



Occurrence. — Apparently rare in the Lyckholm limestone (Fl) at 

 Kertel, island of Dago. 



Holotype.—Csit. No. 57352, U.S.N.M. 



British Museum, thin sections of the type-specimen. 



Family BATOSTOMELLIDiE Ulrich. 



In this family the amalgamate nature of the zocecial walls is most 

 marked, in fact so much so that adjoining walls usually appear 

 as completely fused together. Although the family is well repre- 

 sented in Ordovician strata, species with the most completely amal- 

 gamated walls, such as in Batostomella and Stenopora, are restricted 

 to later Paleozoic rocks. Of the genera discussed in this work, 

 Bythopora, Lioclemella, and Lioclema are typical Batostomellidae. 

 Eichwald's Orhipora is referred to the family on account of its fused 

 walls, while the new genus Estlioniopora is considered as a primitive 

 type of Stenopora. Eridotrypa, although probably best placed in 

 the family, is a somewhat aberrant genus having relations with the 

 H. similis section of Homotrypa. 



Genus BYTHOPORA Miller and Dyer. 



Bythopora Miller and Dyer, Contr. to Pal., No. 2, 1878, p. 6. — ^Miller, North 

 Amer. Geol. and Pal., 1889, p. 295. — Ulrich, Geol. Surv. Illinois, vol. 8, 

 1890, p. 376; Geol. and Nat. Hist. Surv. Minnesota, vol. 3, pt. 1, 1893, p. 

 263; Zittel's Textbook of Paleontology, (Eng. ed.), 1896, p. 277.— Simpson, 

 Fourteenth Ann. Eep. State Geologist of New York for the year 1894, 1897, 

 p. 551.— NiCKLES and Bassler, Bull. 173, U. S. Geol. Surv., 1900, p. 32.— 

 Grabau, Bull. Buffalo Soc. Nat. Sci., vol. 7, 1901, p. 166.— BassLER, Bull. 

 292, U. S. Geol. Surv., 1906, p. 29.— Cumings, Thirty-second Ann.- Rep. 

 Dep. Geol. Nat. Res. Indiana, 1907, p. 741. — Hennig, Archiv fur Zool., 

 vol. 4, No. 10, 1908, p. 44. 



Species of Bythopora are uncommon in American Middle Ordo- 

 vician strata and seem equally scarce in Russia, the following B. sub- 

 gracilis being the only one so far discovered in the roclvs of the lat- 

 ter country. The zoarium in Bythopora consists of slender branches 

 with small, oblique zocecial apertures narrowing above. The zoce- 

 cial interspaces are generally thick and are channeled. Mesopores 

 and diaphragms are few or wanting and acanthopores are never 

 numerous. At the surface the channeled interspaces and elongate 

 aperture are characteristic. 



Genotype. — Bythopora fruticosa Miller and Dyer. Upper Ordo- 

 vician (Maysville) of the Ohio Valley. 



