EAELY PALEOZOIC BEYOZOA OF THE BALTIC PROVIlSrCES. 221 



Occurrence. — The original types of Constellaria varia were found in 

 the Nematopora bed of the Lower Trenton at Cannon Falls, Minne- 

 sota. The species is known from the same general horizon at other 

 American localities, notably in Canada and in Tennessee. In the 

 Russian collections from the Wassalem beds (D3), at Uxnorm, near 

 Reval, a fine, practically complete zoarium of this species occurred, 

 while smaller but equally typical specimens were found in the Jewe 

 limestone (Dl), Baron Toll's estate, near Jewe, Esthonia. 



Plesioty pes. —Cat. Nos. 57300, 57301, U.S.N.M. 



British Museum, thin section of a Russian figured specimen. 



Genus STELLIPORA Hall. 



Stellipora Hall, Nat. Hist. New York, vol. 1, 1847, p. 79.— D'Orbigny, Prodr. 



de Pal., vol. 1, 1850, p. 22. — Ulrich, Journ. Cincinnati Soc. Nat. Hist., vol. 



5, 1882, p. 155; vol. 6, 1883, p. 263; Geol. Surv. Illinois, vol. 8, 1890, p. 374; 



Zittel's Textbook of Paleontology (Eng. ed.), 1896, p. 276. — Nickxes and 



Bassler, Bull. 173, U. S. Geol. Surv., 1900, p. 34. 

 Stellipora (part) Dybowski, Die Chaetetiden d. Ostbaltischen Silur-Form., 1877, 



p. 42.— Miller, North Amer. Geol. and Pal., 1889, p. 203. 



Differs from Constellaria in its incrusting or free lamellate method 

 of growth and in having the interspaces between the raised zooecial 

 clusters composed of mesopores alone. 



Genotype.- — Stellipora antJieloidea Hall. Middle Ordovician (Tren- 

 ton) of New York and Canada. 



From America but a single species of Stellipora, the genotype, has 

 been described, although the collection of the United States National 

 Museum contains several new forms allied to the Russian species. 

 A review of Dybowski's work upon this genus has shown that, while 

 he included Constellaria as a synonym, the two species assigned to 

 Stellipora are typical members of the latter genus as now restricted. 

 The third species noted below is interesting in that it forms large, 

 isolated, star-Hke clusters. With the genotype, the several new 

 American forms, and the three species following, Stellipora has a fair 

 specific representation. 



STELLIPORA REVALENSIS Dybowski. 



Plate 4, figs. 8-86; text fig. 123. 



Stellipora revalensis Dybowski, Die Chaetetiden der Ostbaltischen Silur-Forma- 

 tion, 1877, p. 44, pi. 3, figs. 8a, b. 



Both this and the following species have been described in detail by 

 Dybowski, and I can only verify their reference to Stellipora and add 

 a few notes concerning the specific characters. There are no described 

 American forms with wliich either might be confused. In each spe- 

 cies the zoarium is a small, lamellate expansion with a wrinkled 

 epitheca on the basal side, and with prominent star-shaped clusters 



