CORALS AND BRYOZOA. 
231 
Fistulipora densa. 
NOT FIGURED. 
Thallostigma densa. Hall. Trans. Albany Institute, vol. x, p. 186. 1881. 
“ “ “ Report of State Geologist for 1883, p. 25. 1884. 
Zoarium consisting of thin lamellate expansions incrusting other objects, 
especially Cyathophylloid corals; greatest thickness observed .75 mm. Cell 
apertures broadly oval, sometimes nearly circular, often sub-polygonal, length 
.25 mm., width generally from two-thirds to four-fifths the length, very 
closely and generally irregularly disposed, though sometimes in compara¬ 
tively straight lines ; some portion of the margins of adjacent apertures are 
in contact. Peristomes thin, equally elevated. Mesopores minute, on the 
specimens observed never entirely surrounding an aperture, very frequently 
having the appearance of the interstitial cells of a Monotrypa. When the 
apertures are arranged in lines there are usually two mesopores between 
adjacent apertures longitudinally, but often only one. Surface marked by 
maculae, the centers of which are distant from each other from 2 to 3 mm. ; 
the apertures occupying these are larger and more nearly circular than the 
others, having a diameter of about .30 mm. 
Some portions of the frond resemble F. digitata, but it may be distinguished 
from that species by the larger, sub-polygonal cell apertures, which are never 
entirely surrounded by mesopores, the maculae, composed of larger cell aper¬ 
tures and the absence of prominent nodes: from F. multaculeata it is distin¬ 
guished by the much closer arrangement of cell apertures, the smaller and fewer 
mesopores, which never entirely surround an aperture, the maculae composed 
of larger cell apertures, and the absence of nodes on the peristomes and mar¬ 
gins of mesopores: from F. minuta by the somewhat smaller and much more 
closely disposed cell apertures, fewer and smaller mesopores, and the absence 
of a striated appearance of the surface caused by the peristomes and margins of 
mesopores, a feature which is characteristic of that species: from F. decipiens 
by the more closely disposed cell apertures, the much fewer and smaller meso¬ 
pores; the same features separate it from F. mediopora of the Lower Helder- 
berg group: from F. intercellata, of the Upper Helderberg group, it is distin- 
