220 
PALAEONTOLOGY OF NEW YORK. 
mesopores; in that species the cell apertures are sometimes polygonal, and it 
is frequently difficult to distinguish the apertures from the mesopores: from 
F. confertipora by the smaller and more distant cell apertures: from F. tegens 
by the larger cell apertures and mesopores: from F. minuta by the more distant 
cell apertures and their more irregular disposition: on that species they are 
generally so arranged that the peristomes and margins of the mesopores give a 
striated appearance to the surface of the frond: from F. digitata by the larger and 
more distant cell apertures, the larger mesopores, and the absence of compara¬ 
tively strong nodes between the cell apertures: from F. densa by the larger 
and more distant cell apertures, and the absence of maculae composed of 
larger cell apertures : from F. intercellata, of the Upper Helderberg group, by its 
more nearly circular and more distant cell apertures, thinner peristomes and 
larger mesopores. 
Formation and locality. Hamilton group, Eighteen-Mile creek, Erie county, 
New York. 
Fistulipora micropora. 
PLATE LVII, FIG. 20; AND PLATE LIX, FIG. 3. 
Thallostigma micropora, Halt.. Trans. Albany Institue, vol. x, p. 186. 1881. 
“ “ “ Report of State Geologist for 1883, p. 26. 18S4. 
Zoarium consisting of very thin lamellate expansions, incrusting other objects, 
especially crinoid columns; greatest thickness observed .33 mm. Inter¬ 
cellular tissue vesiculose. Cell apertures broadly oval, frequently nearly 
circular, length about .18 mm. or less; irregularly disposed, varying from 
contact to a space equal to the width of an aperture. Peristomes thin, 
equally elevated, and smooth on the specimens observed. Mesopores minute, 
about ten in the space of 1 mm., generally only one series between adjacent 
apertures, rarely two ; margins of the same height as the peristomes. 
This species may be distinguished from F. segregata by the thinner fronds, 
the smaller cell apertures, their closer arrangement, and the more delicate 
appearance of the surface of the frond: from F. digitata by the different 
manner of growth, the smaller cell apertures, their less frequent occurrence, 
