CORALS AND BRYOZOA. 
267 
length of an aperture; the apertures forming the rows are closely disposed, 
the pustules being in contact and giving to the apertures the appearance of 
being situated on curved elevations or ridges. The marginal apertures are a 
little larger than the others, having a length of about .25 mm. Peristomes 
thin, the posterior portion a little the more prominent and having two 
slight denticulations. There are no longitudinal striations on the specimens 
observed. 
■ag -V- -V,. aa. -V- -V' -Y- -V, aa, 
•yV 'TV -/v - '/v* '/v- '/v w 'A' -yv- 
Formation and locality. Hamilton group, Hill’s gulch, four miles south of 
Le Roy, New York. 
ACROGENIA, Hall. 1881. 
Acrogenia prolifera. 
PLATE LXI1I, FIGS. 7-15. 
Acrogenia prolifera, Hall. Trans. Albany Institute, vol. x, p. 194. 1881. 
“ “ “ Report of State Geologist for 1883, p. 52. 1884. 
Zoarium ramose, branches flattened, proliferous. One frond, which is very 
well preserved, has the following manner of growth: the basal extremity 
for the space of 5 mm. is simple, with several lateral rootlets; it is strongly 
striated, and has a diameter of about 1.25 mm.; this portion bifurcates, the 
two parts very gradually diverge and have frequent lateral striated rootlets, 
the striae somewhat spirally disposed; the ends are conically truncated ; 
from these truncated ends proceed two short growths, both extremities of 
which are conically truncated; from the apices of these proceeds a striated, 
cylindrical stipe, conically truncated at each end, and having a length of 
8 mm., and a diameter of 2 mm.; the striae are of unequal strength, some of 
them extremely fine: from the truncated apex of this stipe proceed apparently 
several branches with conically truncated bases which are at first cylindrical, 
becoming flattened and very gradually expanding: from this point the 
growth is regular, two depressed, quadrangular branches proceeding from 
the truncated extremity of each preceding branch; length of internodes 
