CORALS AND BRYOZOA. 
233 
neath; but on different parts of the frond all the gradations between the 
extremes can be observed. This feature is also characteristic of the allied 
forms F. minuta and F. ? subtilis. 
This species may be distinguished from F. minuta by the larger cell apertures 
and mesopores, and their more irregular disposition ; in that species they are 
very frequently so arranged that the peristomes and margins of mesopores give 
to the surface a striated appearance: from F. ? subtilis it is distinguished by 
the larger size of the apertures and mesopores. 
Formation and locality. Hamilton group, York, Livingston county, N. Y. 
FlSTULIPORA ? SUBTILIS. 
NOT FIGURED. 
Thallostigma subtilis, Hall. Trans. Albany Institute, vol. x, p. 187. 1881. 
“ “ “ Report of State Geologist for 1883, p. 30. 1884. 
Zoarium consisting of extremely thin foliaceous expansions incrusting other 
objects; thickness of observed fronds .25 mm. Cell apertures circular, oval 
or sub-polygonal, diameter or length .16 mm., irregularly disposed, some¬ 
times in contact, at other times separated by three times the diameter of an 
aperture. Peristomes moderately strong, usually equally elevated, and some¬ 
times having a comparatively strong node or spinule. Mesopores usu¬ 
ally from one-half to two-thirds the size of the apertures; margins of the 
same height as the peristomes. The apertures and mesopores are sometimes 
so disposed that their margins give to the surface a striated appearance, and 
it is often difficult to distinguish the cell apertures from the mesopores, the 
frond having the appearance of a Paluschara. 
This species resembles F. decipiens and F. minuta , but may be distinguished 
by its smaller cell apertures and mesopores, and the more delicate appearance 
of the frond. 
Formation and locality. Hamilton group, West Williams, Ontario, Canada. 
Note.—D r. Rominger has described (loc. cit. under F. minuta) five species of Fistulipoka from the 
Hamilton group of Michigan ; two from the same horizon at Widder, Ontario, Canada, and two from Ham¬ 
burg, Erie county, N. Y. I have had no opportunity of comparing the specimens of these species with 
those here described, and the comparison with the descriptions has not always proved satisfactory. 
