CORALS AND BRYOZOA. 
43 
others; very closely arranged in quincunx, nearly in contact: margins very 
thin, scarcely elevated above the surrounding surface. Interapertural space 
flat; granulose. 
The general appearance and arrangement of the cell apertures will distinguish 
this species from any similar form in the same horizon. 
Formation and locality. Lower Helderberg group, near Clarksville, N. Y. 
Thamniscus? Nysa. 
PLATE XXII, FIGS. 31, 32; 47, 48. 
Tlmmniseus Nysa, Hall. Thirty-second Kept. N. Y. State Mus. Nat. Hist., p. 175. 1879. 
“ “ var. Hall. Thirty-second Rept. N. Y. State Mus. Nat. Hist., p. 176. 1879. 
“ “ “ “ Report of State Geologist for 1882. Expl. pi. 22, figs. 31, 32. 1883. 
“ “ Hall. Report of State Geologist for 1882. Expl. pi. 22, figs. 47, 48. 1SS3. 
Zoarium ramose, solid. Bifurcations frequent; branches 1 mm. in diameter, 
very slightly enlarging before bifurcation ; frequently curved. Non-cellulif- 
erous face obscurely striated. Cells tubular, opening directly outward; 
diameter of apertures .15 mm.; disposed in oblique transverse rows ; distance 
between rows equal to the diameter of an aperture, the apertures forming the 
transverse rows nearly or quite in contact: margins thin, strongly elevated. 
Formation and locality. Lower Helderberg group, near Clarksville, N. Y. 
FENESTELLA (Miller), Lonsdale. 1839. 
Fenestella crebripora. 
PLATE XX, FIGS. 1-3. 
Fenestella crebripora, Hall. Twenty-sixth Rept. N. Y. State Mus. Nat. Hist., p. 95. 1874. 
“ “ “ Thirty-second Rept. N. Y. State Mus. Nat. Hist., p. 167. 1879. 
“ “ “ Report of State Geologist for 1882. Expl. pi. 20, figs. 1-3. 1883. 
Bryozoum infundibuliform. Branches slender, rounded or sub-angular, marked 
by very fine striae which are often indistinct. Bifurcations distant from 
4 to 10 mm. Width of interstices greater than that of the branches. Dis¬ 
sepiments slender, often oblique, on the same plane as the branches, five 
in the space of 5 mm. Fenestrules sub-quadrangular, often rhomboidal, 
width usually about one-half the length. 
