EABLY PALEOZOIC BRYOZOA OP THE BALTIC PROVINCES. 107 



SPATIOPORA LINEATA INCEPTA Ulrich. 

 Plate 7, figs. 9, 10. 



Spatiopora maculosa var. incepta Ulrich, Geol. Nat. Hist. Surv. Minnesota, vol. 



3, pt. 1, 1893, p. 320. 

 Spatiopora lineata-incepta Nickles and Bassler, Bull. 173, U. S. Geol. Surv., 



1900, p. 407. 



The Black River (Decorah) shales of Minnesota have yielded sev- 

 eral examples of a species of Spatiopora which was briefly defined by 

 Ulrich as S. maculosa var. incepta. Further study of these specimens 

 showed that they might be classed with more reason as a variety of 

 the middle Cincinnatian form, ^S'. lineata Ulrich. The zoarium of 

 both the Russian and American specimens is a thin crust spread over 

 shells of OrtTioceras (PI. 7, fig. 9). The surface is smooth, but under 

 a hand lens numerous blunt acanthopores are occasionally seen. 

 Maculae are present at regular intervals and contain the only meso- 

 pores which occur. The zooecia are tliin-walled and have little to 

 distinguish them from simple incrusting Trepostomata. Thin sec- 

 tions, however, show the characteristic ceramoporoid structure. 



Occurrence. — Rare in tke upper Black River (Decorah) shales at 

 Chatfi.eld, Minnesota, and in the Wesenberg limestone (E) at Wesen- 

 berg, Esthonia. 



Plesiotype.—Csit. No. 57206, U.S.N.M. 



Genus SCENELLOPORA Ulrich. 



Scenellopora Ulrich, Journ. Cincinnati See. Nat. Hist., vol. 5, 1882, p. 150. — 

 Miller, North Amer. Geol. and Pal., 1889, p. 322. — Ulrich, Geol. Surv. 

 Illinois, vol. 8, 1890, p. 368; Zittel's Textbook of Paleontology (Eng. ed.), 

 1896, p. 268. — Simpson, Fourteenth Ann. Rep. State Geologist of New York 

 for the year 1894, 1897, p. 593.— Nickles and Bassler, Bull. 173, U. S. Geol. 

 Surv., 1900, p. 24. 



This genus was established for a simple, pedunculate, ceramoporoid 

 bryozoan from Middle Ordovician strata of eastern Tennessee. In 

 the type and only described species the upper surface is slightly con- 

 cave and celluliferous, the zooecial aperture occupying the summits 

 of low ridges radiating from the center. A second species with surface 

 characters much as in Eichwald's Ceramopora socialis is known from 

 the same strata holding the type. This new species and C. socialis 

 both agree in being parasitic, differing in that respect from the geno- 

 type, and causing, therefore, a slight revision in the generic diagnosis. 



Genotype. — Scenellopora radiata Ulrich. Middle Ordovician of 

 Tennessee. 



92602*— Bull. 77—11- 9 



