287 
Mesopores are few and seldom observed in shallow tangential sections 
of old specimens. 
Acanthopores are numerous, 2 to 6 about a zooecium, and of two sizes. 
In the tangential sections the walls appear amalgamated and a distinct 
crenulation is observed from the longitudinal section in the axial region. 
Diahpragms are few and unequally distributed in the immature zone 
and close set in the mature where 2 to 4 cross the tube in the space of one 
tube diameter. 
The method of growth of this species distinguishes it from the associated 
forms. 
Occurrence: Ridley limestone, 24% miles northwest of Salem, Rutherford 
County, Tennessee. 
Holotype: 245-6,10. Indiana University. 
Genus Heterotrypa Nicholson. Genotype: Monticulipora frondosa 
D’Orbigny. Heterotrypa (in part) Nicholson, Pal. Tabulate Corals, 1879, 
p. 291; genus Monticulipora, 1881, pp. 101, 103. Zittel, Handb. Pal., 1, p. 615. 
Ulrich, Jour. Cincinnati Soc. Nat. Hist., 5, 1882, p. 155; ibid., 6, 1883, p. 83. 
Foord, Contr. Micro-Pal. Cambro-Sil., 1888, p. 20. Ulrich, Jour. Cincinnati 
Soc. Nat. Hist., 6, 1883, pp. 83-85. Roemer, Leth. geog., pt. 1, Leth. Pal., 
1883, p. 471. Rominger, Amer. Geol., 6, 1890, pp. 114, 119. Ulrich, Geol., 
Surv. Ill., 8, 1890, pp. 371, 413; Geol. Minnesota, 3, 1893, p. 267. Zittel’s 
Textb. Pal. (Engl. ed.), 1896, p. 104. Ulrich, Zittel’s Textb. Pal. (Engl. ed.), 
1896, p. 273. Simpson, 14th Ann. Rept. State Geol. New York for 1894, 1897, 
p. 579. Nickles and Bassler, Bull. U. S. Geol. Sury., 173, 1900, p. 31. Cum- 
ings, Amer. Geol., 29, 1902, p. 199. Ulrich and Bassler, Smith. Mise. Coll., 
Quart., 47, 1904, pp. 24, 25. Bassler, Zittel-Eastman Textb. Pal., 1913, p. 333. 
Zoarium erect (ramose or) frondescent ; acanthopores of one kind; small ; 
mesopores varying in number, generally abundant, sometimes wanting 
almost entirely. With the addition of the words enclosed in parenthesis the 
description of the genus is taken from the ‘‘Revision of the Paleozoic Bry- 
0zoa”’ by Ulrich and Bassler. 
Heterotrypa patera n. sp. Plate VI, Figs. 5-6. Zoarium ramose, about 5 
to 10 mm. in diameter. Surface is smooth, with small maculae composed 
of mesopores, surrounded by zooecia slightly larger than the average; about 
4in 4 sq. em. 
Tangential sections show the zooecia to be subcircular and thick-walled. 
A very thick cingulum consisting of laminated secondary tissue, surrounds 
each aperture. A thin dark line separates the cingulum from the true zooe- 
cial wall which forms an angular boundary between the zooecia and appears 
finely granular, light colored and amalgamated. The acanthopores are 
small, with a distinct, minute central lucid spot and an indefinite outer 
boundary ; 5 to 10 among 10 zooecia. 
The zooecia in the axial region are crossed by diaphragms from 1 to 35 
tube-diameters apart. From the immature region the zocecial tubes proceed 
outward in a gradual curve, increasing sufficiently in the peripheral zone to 
cause the zooecia to open perpendicularly at the surface. The walls and 
cingulum increase in thickness from the early mature region to the peri- 
