EAELY PALEOZOIC BEYOZOA OF THE BALTIC PEOVINCES. 207 

 DEKAYELLA PRffiNUNTIA SIMPLEX Ulrich. 



Text fig. 111. 



Dekayella prsenuntia var. simplex Ulkich, Geol. and Nat. Hist. Surv. Minnesota, 

 vol. 3, pt. 1, 1893, p. 271, pi. 23, figs. 39-42. 



This variety, which, as noted before, is best represented in the 

 Russian collections, may be distinguished from the t3rpical form, first, 

 by the scarcity of mesopores, second, by its rather thick-walled, 

 polygonal zooecia, and third, by the few and rather poorly developed 

 acanthopores. The two sets of acanthopores characteristic of Dekay- 

 ella are distinguished with difiiculty. In vertical sections, aside 

 from the practical absence of mesopores, no differences can be noted 

 between this and the typical form. 



Occurrence. — ^The American types are from the Black River 

 (Decorah) shales, at Minneapolis and St. Paul, Minnesota. Very 

 abundant in the Wassalem beds (D3) at Uxnorm, Esthonia (Cat. No. 

 57291, U.S.N.M.). 



British Museum, specimens and thin sections from Uxnorm. 



DEKAYELLA PRENUNTIA N^VIGERA Ulrich. 



Dekayella prsenuntia var. nsevigera Ulrich, Geol. and Nat. Hist. Surv. Minne- 

 sota, vol. 3, pt. 1, 1893, p. 271. 



This form is much like the preceding variety simplex and differs 

 mainly in having conspicuous groups of maculae composed of numer- 

 ous mesopores. Other differences are thinner zocecial walls and a fre- 

 quently inosculating form of growth. The Russian specimens are 

 small fragments of zoaria and do not show such frequent branching, 

 but otherwise they are identical with the Minnesota forms. 



Occurrence. — Rare in the Wassalem beds (D3) at Uxnorm, Esthonia 

 (Cat. No. 57292, U.S.N.M.). The American form was found in the 

 Black River (Decorah) shales of Minnesota. 



British Museum, specimen and thin section from Uxnorm. 



Genus LEPTOTRYPA Ulrich. 



Leptotrypa Ulrich, Jonrn. Cincinnati Soc. Nat. Hist., vol. 6, 1883, p. 158. — 

 Miller, North Amer. Geol. and Pal., 1889, p 311. — Ulrich, Geol. Surv. 

 Illinois, vol. 8, 1890, pp. 377, 455; Geol. and Nat. Hist. Surv. Minnesota, 

 vol. 3, pt. 1, 1893, p. 316. — Simpson, Fourteenth Ann. Rep. State Geol. New 

 York for the year 1894, 1897, p. 580.— Nickles and Bassler, Bull. 173, U. S. 

 Geol. Surv., 1900, p. 31. — Ulrich and Bassler, Smiths. Misc. Coll., vol. 47, 

 1904, pp. 24, 28. — CuMiNGS, Thirty-second Ann. Rep. Dept. Geol, Nat, Res. 

 Indiana, 1907, p. 749. 



Heterotrypidse with the zoarium of thin, evenly spread, parasitic 

 expansions with thin-walled, polygonal zooecia, no mesopores, few 

 diaphragms, and very small acanthopores, which are never abundant. 



Genotype. — Leptotrypa minima Ulrich. Upper Ordovician (Mays- 

 ville), Ohio Valley. 



