EARLY PALEOZOIC BEYOZOA OF THE BALTIC PROVINCES. 205 



the HeterotrypidsB in just these two respects. Both the Batosto- 

 meUidse and the Constellariidse have diaphragms instead of cysti- 

 phragms, thus differing from the MonticuUporidse, but the first men- 

 tioned has thick walls with a number of them so fused together that 

 the individual wall common to adjacent zooecia is not clearly distin- 

 guishable. The Constellariidse differs from all the Amalgamata 

 f amUies in the nature of its acanthopore, which is small and granular. 

 Although the famUy differences mentioned above are few and 

 apparently slight, they are known from the study of a host of species 

 to be fundamental and of as great value as more detailed discrimina- 

 tions founded upon Hving forms. 



Genus DEKAYELLA Ulrich. 



Dekayella Ulrich, Jonm. Cinciimati Soc. Nat. Hist., vol. 5, 1882, p. 155; vol. 

 6, 1883, p. 90. — Miller, North Amer. Geol. and Pal., 1889, p. 184. — Ulrich, 

 Geol. Surv. Illinois, vol. 8, 1890, p. 372; Geol. and Nat. Hist. Surv. Minne- 

 sota, vol. 3, pt. 1, 1893, p. 269; Zittel's Textbook of Paleontology (Eng. ed.), 

 1896, p. 273. — Simpson, Fourteenth Ann. Rep. State Geologist New York 

 for the year 1894, 1897, p. 589.— Nickxes and Bassler, Bull. 173, U. S. 

 Geol. Surv., 1900, p. 31. — Cumings, American Geologist, vol. 29, 1902, p. 

 200.— Ulrich and Bassler, Smiths. Misc. Coll., vol. 47, 1904, pp. 24, 27. 



Heterotrypidse with an erect ramose or frondescent zoarium made 

 up of rather thin-walled zooecia, usually abundant mesopores, both 

 kinds of tubes crossed by numerous diaphragms; acanthopores in 

 two sets, large and small. 



The presence of two sets of acanthopores in Dekayella is the only 

 distinction between this genus and Heterotrypa, but as this character 

 pertains to a dozen or more species ranging through the middle and 

 upper Ordovician, it is believed to be of generic importance. The 

 two sets of acanthopores are distinctly visible only in the mature 

 zone of the zoarium, so that tangential sections which cut other parts 

 of the specimen will not show this feature. 



Genotype. — Dekayella ohscura Ulrich. Upper Ordovician (Eden) of 

 the Ohio Valley. 



DEKAYELLA PRffiNXJNTIA Ulrkh. 



Text fig. 111. 



Dekayella prsenuntia Ulrich, Geol. and Nat. Hist. Surv. Minnesota, vol. 3, pt. 

 1, 1893, p. 270, pi. 23, figs. 32-37.— Simpson, Fourteenth Ann. Rep. State 

 Geologist of New York for the year 1894, 1897, p. 589, figs. 177-179. 



The Wassalem beds at Uxnorm have afforded numerous specimens 

 of a Dekayella so similar to the typical D, prxnuntia Ulrich, and some 

 of its varieties, that I am unable to point out any distiuguishing 

 characters. Most of the Russian specimens have the characteristics 

 assigned to D. prsenuntia var. simplex Ulrich, a form in which the 

 mesopores are reduced to a minimum number, the zooecial apertures 



