240 PALEONTOLOGY OF NEW YORK. 



somewhat regular intersecting rows. Peristomes strong, equally elevated. 

 The surfjice 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 Fistuupora 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 Ptilodidya 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, Ontcirio, Canada. 



CERAMELLA, nov. gen. 

 Ceramella scidacea, n. sp. 



PLATE IjaV, FIGS. 8-8. 



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, ejich 

 one having a length of from 3 to 5 mm., and a width of 1 mm., often lenti- 



