286 
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 apart. 
The irregular distributed zooecia and mesopores, 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 Heterotrypidae 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- 
tinetly 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, 18838, 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. 278. Simpson, 14th Ann. Rep. State Geol. New York for 1894, 1897, 
p. 589. Nickles and Bassler, Bull. U. S. Geol. Surv., 178, 1900, p. 31. Cum- 
ings, Amer. Geol., 29, 1902, p. 200. Ulrich and Bassler, Smiths. Mise. 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 acanthopores, large 
and small; mesopores variable, generally more or less numerous; dia- 
phragms numerous.” 
Dekayella ridleyana. 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 SO mm. 
The surface is even and maculae of large mesopores are small and incon- 
spicuous. 
The zooecia are polygonal, thick walled; 9 to 91% apertures in 2 mm. 
