28G 



of zooecia slightly larger than the average and less number of mesopores 

 than are present in the intermacular area, occur on the surface at intervals 

 of 2 mm. 



Mesopores are abnudant, slightly beaded, irregular in shape, size and 

 distribution ; about 15 diaphragms cross the tubes in the distance of one mm. 



The zooecia are relatively thin-walled, subcircular or polygonal, in con- 

 tact on 2 or 3 sides mostly, less frequently on four ; 7 or 8 occur in 2 mm. 



The acanthopores are few and of medium size. There are rarely more 

 than one or two in two square mm. The central lucid spot is distinct ; the 

 outer boundary is definite. 



Curved and horizontal diaphragms are present throughout the zooecial 

 tube, separated from % to 1 tube-diameter apai't. 



The irregular distributed zooecia and mesoiwres. the few acanthopores of 

 medium size, and form of zoarium are distinguishing combination of char- 

 acters for this species. 



Occurrence : Pierce limestone, Murfreesboro, Tennessee. 



Holotype: (93) U. S. Nat. Mus. 



Family Hcterotrj/pidaG Ulrich. 



This family includes those trepostomatous bryozoans having zooecia with 

 straight diaphragms, clearly defined acanthopores. and walls of a dual char- 

 acter; the outer wall is amalgamated with the outer one of the adjacent 

 zooecia and shown as a light colored band lying between the inner and dis- 

 tinctly zooecial walls of darker and finely laminated tissue. 



Dekayella Ulrich. Genotype : Dekayella obscura Ulrich. Dekayella 

 Ulrich, Jour. Cincinnati Soc. Nat. Hist., 5, 1882, p. 155 ; ibid., 6, 1883, p. 90. 

 Miller, N. A. Geol. Pal., 1889, p. 184. Ulrich, Geol. Surv. Illinois, 8, 1890, 

 p. 372; Geol. Minnesota, 3, 1893, p. 269; Zittel's Textb. Pal. (Engl, ed.), 

 1896, p. 273. Simpson, 14th Ann. Rep. State Geol. New York for 1894. 1897, 

 p. 589. Nickles and Bassler, Bull. U. S. Geol. Surv., 173. 1900, p. 31. Cum- 

 ings, Amer. Geol., 29, 1902, p. 200. Ulrich and Bassler, Smiths. Misc. Coll., 

 47, 1904. p. 24-27. Grabau and Shimer. N. A. Index Fossils, 1, 1907, p. 132. 

 Bassler, Bull. U. S. Nat. Mus., 77, 1911, p. 205 ; Zittel-Eastman Textb. Pal., 

 1913, p. 333. 



This genus has been briefly and adequately described by Ulrich and 

 Bassler in 1904 as follows : 



"Zoarium erect, ramose or frondescent ; two sets of acanthoiwres, large 

 and small ; mesopores variable, generally more or less numerous ; dia- 

 phragms numerous." 



Dekayella ridlcyana. n. sp. Plate VI, Figs. 3-4. The zoarium consists of 

 large, thick, irregular fronds. The type specimen varies from 8 to 12 mm. 

 in thickness. The greatest observed height is 80 mm. 



The surface is even and maculae of large mesopores are small and incon- 

 spicuous. 



The zooecia are Dolygonal, thick walled ; 9 to 9M> apertures in 2 mm. 



