CORALS AND BRYOZOA. 213 



diameter about .25 mm., irregularly disposed, generally distant from each 

 other a little more than their diameter. Peristomes strong, equally elevated, 

 granulose when well preserved. Mesopores large, frequently equal in size to 

 the cell apertures ; margins elevated slightly less than the peristomes. Sur- 

 face marked by sterile maculae of 1 to 2 mm in diameter, occurring at ir- 

 regular intervals, the cell apertures immediately adjacent not larger than the 

 others. 



• The characteristics of this species are the absence of monticules and the 

 comparatively distant cell apertures. It may be distinguished from F. serrulata 

 which it resembles in size and frequency of the cell apertures, by the absence 

 of monticules and conspicuous opercula : from F. variapora and F. confertipora 

 by the absence of monticules and by its large mesopores. 



Formation and localities. Hamilton group, Eighteen-Mile creek, Erie county, 

 and Bellona, Yates county, N. Y. 



FiSTUUPORA UMBILICATA. 



MOT FiaURBD. 



Thallostigma umbilicata. Hall. Trana. Albany Institute, vol. x, p. 185. 1881. 



" " " Report of State Geologist for 1883, p. 22. 1884. 



ZoARiUM consisting of free or incrusting lamellate expansions, or of masses 

 formed by the superimposition of successive layers of growth ; greatest 

 thickness of the fronds observed 1.50 ram. ; under surface consisting of an 

 epitheca with strong concentric wrinkles. Cells tubular, cylindrical, 

 rectangular or slightly oblique to the surface, usually opening directly 

 outward. Intercellular space vesiculose; near the base the vesicles are 

 irregularly disposed, above they are regularly superimposed. Cell apertures 

 circular, diameter about .30 mm., irregularly disposed, usually distant about 

 three-fourths the diameter of an aperture. Peristomes strong, equally 

 elevated, smooth. Mesopores variable in size, sometimes minute, at other 

 times nearly as large as the cell apertures ; margins slightly elevated, some- 

 times continuing upon the peristomes and giving them a strongly striated 

 appearance. Surface marked by broad, rounded monticules, the centers of 



