CORALS AND BRYOZOA. 
283 
The concave central space, lying between the ridges of apertures, and be¬ 
tween the zoaria forming the colony, is bullate ; the bullae in the central space 
have a diameter of from .15 to .25 mm. and are polygonal; those between 
the ridges are much smaller, having a diameter of from .6 to .10 mm.; those 
between the individual zoaria are of two kinds, one circular or sub-polygonal 
from mutual pressure, the diameter generally from .50 to .60 mm., rarely a 
little more; these are very frequently in contact, and when separated the 
space between them is occupied by bullae similar to those between the 
celluliferous ridges. When the surface becomes worn the upper walls of the 
bullae or vesicles are worn or broken away, they have the appearance of 
shallow pits. 
This genus is very similar to some forms of the genera Radiopora, or Actino- 
pora, of D’Orbigny. (Paleontologie Francaise; Cretaceous Bryozoa. Plates 
644 and 649.) 
Formation and localities. Hamilton group, Le Roy, N. Y., and West Williams, 
Ontario, Canada. 
PTILOPORA, McCoy. 1849. 
Ptilopora striata. 
PLATE LXVI, FIGS. 30-33. 
Ptilopora striata, Hall. Trans. Albany Institute, vol. x, p. 190. 1 SSI. 
“ “ “ Report of State Geologist for 1SS3, p. 58. 1S84. 
Zoarium consisting of a strong stipe or midrib, proceeding from a spreading 
base, or from rootlets attached to foreign bodies, and having slender equi¬ 
distant lateral branches, connected by slender processes or dissepiments ; 
celluliferous on one face only. The base of the stipe has a width of 1.50 mm. or 
more, gradually tapering to .25 mm.; transverse section circular or broadly 
oval; lateral branches .25 mm. in width, uniform in size, diverging from 
the midrib at an angle of about forty-five degrees, regularly distant a little 
less than twice the width, seven in the space of 5 mm., transverse section 
broadly oval or circular. 
On the non-celluliferous face the midrib and branches are rounded and 
striated; on the lateral branches the striae are of uniform size, five or six 
