EABLY PALEOZOIC BRYOZOA OF THE BALTIC PROVINCES. 155 



honor of Miss Francisca Wieser, to whom I am indebted for many- 

 drawings illustrating this work. 



Occurrence. — Not uncommon in the thin limestone layers and in 

 the clays of the Wassalem beds (D3) at Uxnorm, Esthonia. 



Coty^es.—Qsii. No. 57249, U.S.N.M. 



Specimens in the collection of the British Museum. 



Genus NEMATOPORA Ulrieh. 



Nematopora Uleich, American Geologist, vol. 1, 1888, p. 234; Geol. Siirv. Illinois, 

 vol. 8, 1890, pp. 401, 644; Geol. and Nat. Hist. Surv. Minnesota, vol. 3, pt. 1, 

 1893, p. 204; Zittel's Textbook of Paleontology (Eng. ed.), 1896, p. 281.— 

 Simpson, Fourteentli Ann. Rep. State Geol. New York for the year 1894, 1897, 

 p. 553.— NiCKLES and Bassler, Bull. 173, U. S. Geol. Surv., 1900, p. 43.— 

 Basslek, Bull. 292, U. S. Geol. Surv., 1906, p. 58. 



Numerous specimens of Nematopora have been observed in the 

 Russian collections, all 

 of which have proved to 

 belong to species de- 

 scribed from North 

 America. The most con- 

 spicuous feature of this 

 genus, separating it from 

 the other genera of the 

 Arthrostylidse, is that 

 the zoarium is continu- 

 ous and dichotomously 

 branched, with the 

 jointed character either 

 limited to the basal ex- 

 tremity or wanting en- 

 tirely. The zooecial char- 

 acters are evident from 

 the various figures shown 

 on the following pages. 



Genotype. — Nematopora ovalis Uhich 

 ton) of the United States and Russia. 



Fig. 76.— Nematopora delicattjla and N. constteta. a, zo- 

 arium NATURAL SIZE AND X18, OF NEMATOPORA DELICATULA; 

 b, TRANSVERSE SECTION OF SAME. GIRARDEAU LIMESTONE 

 DIVISION OF THE RICHMOND GROUP, ALEXANDER COUNTY, 



Illinois. (After Ulrich.) c and d, two fragments, nat- 

 ural SIZE AND X18, OF THE TRENTON SPECIMENS REFERRED BY 



Ulrich to N. delicatula and here renamed N. consueta. 

 Lower part of Trenton limestone, near Cannon Falls, 

 Minnesota. (After Ulrich.) 



Middle Ordovician (Tren- 



NEMATOPORA CONSUETA, new name. 



Text fig. 76. 



Nematopora delicatula Ulrich, Geol. Nat. Hist. Surv. Minnesota, vol. 3, pt. 1, 



1893, p. 206, pi. 3, figs. 26, 27. 

 Not Nematopora delicatula Ulrich, Geol. Surv. Illinois, vol. 8, 1890, p. 646, pi. 



29, figs. 11-116. 



The delicate bryozoan for which the above new name is proposed 

 has been confused with a very similar minute species described from 

 rocks at the base of the Cincinnati group in Alexander County, 



92602°— Bull. 77—11 12 



