226 BULLETIN 77, UNITED STATES NATIONAL MUSEUM. 



best preserved specimens have been prepared, and all agree in the 

 characters here illustrated. In vertical sections the zooecial walls 

 are thin, slightly crenulated, and only occasionally show as definite 

 sharp lines, usually being represented by a diffuse granular structure. 

 The mesopores differ from the zooecia only ui size and in being 

 possibly more granular in structure. Diaphragms are few m both 

 sets of tubes, the average number in each being represented in the 

 figured vertical sections. Tangential sections show the same indefi- 

 nite wall structure, and, in addition, exhibit numerous granular 

 structures, possibly representing acanthopores, in the most mature 

 region. 



The species described by Eichwald as Heteropora giblosa from 

 the Orthoceras limestone at Pulkowa, appears to be based upon a 

 monticulated zoarium of the present form. Without an examina- 

 tion of Eichwald's type the matter of course can not be settled defi- 

 nitely, but in order to avoid a possible synonym, I have given the 

 form here described the same specific name. 



The small, massive zoarium with rather large zooecia isolated by 

 minute mesopores, and the numerous granules of the surface are 

 external characters which alone will identify the species. Internally 

 the structure is too difl'erent from any other form to require com- 

 parison. 



Occurrence. — ^Abundant in the Giauconite limestone (B2) at Reval 

 and vicinity, in Esthonia, and at Pawlovsk, Tswos, on the Wolchow 

 River, localities on the Ladoga Canal, and Wassilkowa, government 

 of St. Petersburg; in the Orthoceras limestone (B3), at Pawlovsk, 

 and in the Echinospherites limestone (Cl), 4 miles east of Reval, 

 Esthonia. 



Cotypes.— Cat. Nos. 57305 to 57313, U.S.N.M. 



British Museum, specimens and thin sections from the Giauconite 

 limestone, Reval. 



Genus DIANULITES Eichwald. 



Dianulites Eichwald, Zool. Spec, vol. 1, 1829, p. 180; Lethsea Rossica, vol. 

 1, 1860, p. 487. — Dybowski, Die Chaetetiden der Ostbaltischen Silur- 

 Formation, 1877, p. 14.— Nicholson, Genus Monticulipora, 1881, pp. 20, 

 155.— Waagen and Wentzel, Pal. Indica, ser. 13, 1886, p. 874. — Simpson, 

 Fourteenth Ann. Rep. State Geol. New York for the year 1894, 1897, p. 

 587.— NiCKLES and Basslee, Bull. 173, U. S. Geol. Surv., 1900, p. 230. 



Hexaporites Pandee, Beitr. zur Geogn. d. russ. Reichs., 1830, p. 106, pi. 1, fig. 

 5; pi. 28, fig. 8. 



Although this name has been frequently quoted, the status of 

 the genus is indicated by the following note published by Nickles 

 and Bassler in their Synopsis of American Fossil Bryozoa: ^ 



1 Bull. 173, U. S. Geol. Surv., 1900, p. 231. 



