240 
PALAEONTOLOGY OF NEW YORK . 
somewhat regular intersecting rows. Peristomes strong, equally elevated. 
The surface between the apertures, and a space about .70 mm. wide bordering 
each fenestrule, is occupied by minute angular pits ; generally only one or two 
series between adjacent apertures, about twelve in the space of 1 mm.; mar¬ 
gins about one-half the thickness of the peristomes and elevated equally with 
them. The non-celluliferous space at the posterior end of the fenestrule is 
always wider than at the anterior end. 
This genus bears the same relations to the genus Coscinium that Intrapora 
does to Stictopora or Fistulipora to Lichenalia. The manner of growth and 
structure is the same, except that the interapertural surface and a space 
bordering the fenestrules is occupied by angular pits or mesopores. It bears a 
very close resemblance to Ptilodictya cosciniformis, of Nicholson, but may be dis¬ 
tinguished by the circular, and more distant cell apertures, and somewhat smaller 
fenestrules; in that species the apertures are elongate-oval and nearly or quite 
in contact: from Coscinium striatum it is distinguished by the presence of inter¬ 
apertural pits, and the absence of denticulations. 
Formation and locality. Hamilton group, Widder, Ontario, Canada. 
CERAMELLA, nov. gen. 
Ceramella scidacea, n. sp. 
PLATE LXXV, PIGS. 5-8. 
Zoarium consisting of an extremely thin foliaceous frond, proceeding from a 
spreading base, greatest thickness observed .30 mm. Celluliferous on each 
face. Cells tubular, arising very obliquely from the mesotheca. Intercel¬ 
lular tissue probably vesiculose. Cell apertures circular or very broadly oval, 
oblique, diameter .25 mm., seldom separated by more than half the diameter 
of an aperture, regularly disposed in quincunx order, alternating and imbri¬ 
cating. Peristomes strong, the upper portion of the cell wall carinated and 
frequently exposed for two-thirds its entire length, the carina sometimes 
projecting very slightly over the aperture. Surface marked by elongate 
depressed maculae, which are sometimes disposed in alternating rows, each 
one having a length of from 3 to 5 mm., and a width of 1 mm., often lenti- 
