CORALS AND BRYOZOA. 233 



neath ; but on different jmrts of the frond all the gradations between the 

 extremes can be observed. This feature is also characteristic of the allied 

 forms F. minuta and F. ? subtilis. 



This species may be distinguished from F. minuta by the larger cell apertures 

 and mesopores, and their more irregular disposition ; in that species they are 

 very frequently so arranged that the peristomes and margins of mesopores give 

 to the surface a striated appearance : from F. ? subtilis it is distinguished by 

 the larger size of the apertures and mesopores. 



Formation and locality. Hamilton group, York, Livingston county, N. Y. 



FiSTULIPORA ? SUBTILIS. 



NOT FIGURED. 



Thcdlmtigma snJbtilix, Hall. Trans. Albany Institute, vol. x, p. 187. 1881. 



Report of State Geologist for 1883, p. 30. 1884. 



ZoARiUM consisting of extremely thin foliaceous expansions incrusting other 

 objects ; thickness of observed fronds .25 mm. Cell apertures circular, oval 

 or sub-polygonal, diameter or length .16 mm., irregularly disposed, some- 

 times in contact, at other times separated by three times the diameter of an 

 aperture. Peristomes moderately strong, usually equally elevated, and some- 

 times having a comparatively strong node or spinule. Mesopores usu- 

 ally from one-half to two-thirds the size of the apertures ; margins of the 

 same height as the peristomes. The apertures and mesopores are sometimes 

 so disposed that their margins give to the surface a striated appearance, and 

 it is often difficult to distinguish the cell apertures from the mesopores, the 

 frond having the appearance of a Paleschara. 



This species resembles F. decipiens and F. minuta, but may be distinguished 

 by its smaller cell apertures and mesopores, and the more delicate appearance 

 of the frond. 



Formation and locality. Hamilton group. West Williams, Ontario, Canada. 



NoTB. — Dr. Rominger has described (loc. cit. under F. minuta) five species of Fistdlipora from the 

 Hamilton group of Michigan ; two from the same horizon at Widder, Ontario, Canada, and two from Ham- 

 burg, Erie county, N. Y. I have had no opportunity of comparing the specimens of these species with 

 those here described, and the comparison with the descriptions has not always proved satisfactory. 



