244 
PALEONTOLOGY OF NEW YORK. 
directly outward. Intercellular space occupied by irregularly disposed 
vesicles. Cell apertures oval, length about .18 mm., width two-thirds the 
length, disposed in regular longitudinal rows, about eight rows on each 
face of the branch; apertures of the marginal rows slightly larger than 
the others, and are sometimes indistinctly trilobate in form. Peristomes 
thin, distinctly and equally elevated, usually smooth, but sometimes with 
indications of slight denticulations on the posterior wall. The non-celluli- 
ferous margin and interapertural space are marked by thin sharp striations, 
which are elevated equally with the peristomes; from two to four striations 
between adjacent ranges of apertures, often presenting an irregular appear¬ 
ance: the lower portion of the frond, for the space of 10 mm. or more, is 
very frequently entirely covered by the striations, and sometimes nearly the 
entire frond is similarly marked, the cell apertures sometimes faintly show¬ 
ing beneath, but very often they are obsolete or covered. 
This species may be distinguished from S. incisurata by the more nearly par¬ 
allel margins and ranges of apertures, the finer and more numerous longitudinal 
striations, the narrower and finely striated non-celluliferous margin which is 
entire, never notched or serrated. It most nearly resembles S. tumulosa, 
but may be distinguished by the larger, more oval cell apertures, which never, 
so far as observed, have a pustuliform appearance, and by the more numerous 
longitudinal striations over the greater portion of the frond: from S. incras- 
sata., by its more slender form, smaller cell apertures, narrower non-celluliferous 
margin, and the numerous longitudinal striations: from S. rigida, of the Upper 
Helderberg group, by the less rigid appearance of the frond, the flat inter¬ 
apertural space, and the finer, more numerous striae: from S. crescens, by the 
presence of fine striations in place of prominent ridges: from <8. interstriata, by 
the coarser and continuous longitudinal ridges: from the other species, at 
present known, from the Lower and Upper Helderberg and Hamilton groups, 
it may be distinguished by the flat interapertural space, and the fine, some¬ 
what irregular longitudinal ridges. 
Formation and localities. In the shales of the Hamilton group, Moscow, Liv¬ 
ingston county, and near Canandaigua Lake, N. Y. 
