58 BRYOZOAN FAUNA OF THE ROCHESTER SHALE. 
Family RHABDOMESONTID^] Vine. 
Genus ACANTHOCLEMA Hall. 
Zocecial tubes arising from a filiform axis in the center of the slender, ramose branches; 
apertures oval, in diagonally intersecting or linear series; acanthopores generally numerous. 
ACANTHOCLEMA ASPERUM (Hall). 
PI. XXI, figs. 3-5; PI. XXIV, figs. 7-9; PI. XXV, figs. 17-20. 
Trematopora aspera Hall, Nat. Hist. New York, Pal. II, 1852, p. 154, pi. 40A, figs. 10 a-c. 
Ratostomella? aspera Nickles and Bassler, Bull. ('. S. Geol. Survey No. 173, p. 189. 
Zoarium of small cylindrical ramulets about 1 nun. in diameter. Surface smooth but, 
under a lens, hirsute because of the numerous acanthopores. Zocecial apertures oval or 
elongate elliptical, usually 0.25 mm. in their longer diameter and 0.10 in the shorter, 4 in 
2 mm. measuring lengthwise, arranged in rather regular longitudinal rows, of which there 
are 7 in 2 mm. Acanthopores numerous, as many as <S or 10 surrounding an aperture and 
often inflecting it. 
The main features brought out in vertical sections are the growth of the zooecial tubes 
from a filiform axis, the small inferior hemiseptum, and the thick, laminated deposit of the 
interzocecial spac< s traversed by the acanthopon s. Tangential sections through the mature 
region show the numerous acant hopor< S and t hick int; rzooecial tissue, while deeper sections 
reveal the rhomboidal shape of the primitive zocecia. 
This very abundant species might be confused with the equally abundant Batostomettti 
granvlifera, bul the larger zoaria, smaller and more numerous acanthopores, less regularly 
arranged zocecia, and interzooecial spaces occupied by mesopores are points of differences 
Internally thi two are widely different. 
Occurrence. — Rochester shale at Lockport, Rochester, and Niagara Falls, N. Y.; Grimsby, 
Hamilton, mid Thorold, Ontario; Osgood beds at Osgood, lud. 
Catalogue numbers, 35756, HI 1'.), U. S. National Museum. 
Family A.RTHROSTYLID^E Uirich. 
Genus NEMATOPORA Uirich. 
The following is a well-developi d sp< en s of (his genus, differing but little from some ol 
the Ordovician forms. Nematopora \< distinguished from other members of the Arthrtijj 
stylidse in that the zOai ium is continuous instead of jointed above the pointed basal extremity. 
Nematopora mini 'i a (Hall). 
PI. XV11I, tig. 10, Pi. XXI, tigs. sll. 
Trematopora ? ( Trachypora) minutu Hall, Twenty-eighth Ann. Kept. New York State Mus. (doc.ed.i 
pi. 11, fig. 8. 
Tn mutopora minutu Hall, Twenty-eight li Ann. Kept. New York State Mus. (Mus. ed.), p. 113, pi. 11 
fig. 8. 
trematopora minutu Hall, Eleventh Ann. Kept. Indiana Geol. Nat. Hist., p. 234, pi. 10, fig. 8. 
Nematopora minuta Uirich, Geol. Survey Illinois, Vlll, p. 645. 
In the Rochester shale collections numerous examples of a single species of Nematopori 
have been observed, which, upon comparison with the type of Hall's Trematopora minuta 
from the Niagaran at Waldron, Ind., have proved to belong to the same species. 
Original description— Biyozoum ramose very slender; branches frequent, widely diverging; diame 
ter, 0.5 millimeter. Cell apertures elongate-oval, length about 0.4 mm., and width 0.2 mm.; distant 
from each other longitudinally about equal to the length ot an aperture, arranged in spiral rows a Ions 
the branch. Margins distinctly elevated and granulose, and separated from each other by tortuod 
lines of nodes. 
To the above description may be added the following: The zoarium is ramose, but, th 
lower end is pointed lor attachment in a base spread over other objects. Measuring lonflj 
