270 
PALAEONTOLOGY OF NEW YORK. 
The surface characters are somewhat similar to those of Stictopora rhomboidea 
of the Upper Helderberg group, but the manner of growth will readily serve 
to distinguish it. From all other species, at present known, it may be distin¬ 
guished by the clavate form of the frond. 
Formation and locality. Hamilton group, Kashong creek, Bellona, Yates county, 
N. Y. 
PTILODICTYA, Lonsdale. 1839. 
(See page 38.) 
Ptilodictya parallela, n. sp. 
PLATE LXI, FIGS. 7, 8. 
Zoarium consisting of a simple stipe, having an acute base, transverse section 
near the base circular, striated, rapidly enlarging and becoming flattened 
above ; stipe about 3 mm. in width, the margins for the greater portion of the 
length essentially parallel; transverse section lenticular, greatest thickness 
about .50 mm. Cells tubular, arising obliquely from the mesotheca, curving 
and opening directly outward; the marginal cells are slightly oblique to the 
axis of the frond, the others are parallel. The intercellular tissue has not 
been observed. Cell apertures circular, diameter about .20 mm., disposed 
in longitudinal parallel rows, from ten to twelve on a branch, the apertures 
of the rows are separated by a little less than their diameter; in the 
central rows there are sixteen apertures in the space of 5 mm.; in the 
marginal rows twelve in the same space. Peristomes thin, slightly elevated, 
the posterior portion the most prominent, and with two minute denticula- 
tions. Ranges of apertures separated by smooth prominent ridges, about 
one-third the width of the cell apertures; the ridge along the middle of the 
branch is stronger than the others and sometimes has the appearance of a 
carina. 
Formation and localities. Hamilton group, Darien Centre, Genesee county, and 
near the head of Canandaigua lake, Ontario county, N. Y. 
