CORALS AND BRYOZOA. 215 



Cell apertures circular, diameter .30 mm., irregularly disposed, usually dis- 

 tant from each other about the diameter of an aperture ; apertures usually 

 operculate, the opercula rounded or conical at the centers, with five or six 

 ridges radiating from the center to the peristomes. Peristomes strong, 

 equally elevated, the striations of the cell walls extending over their mar- 

 gins and giving them a serrulate appearance. Mesopores large, their diameter 

 being frequently more than that of the cell apertures; margins slightly 

 elevated, and when well preserved granulose. 



Surface marked by low, rounded maculae, the centers of which are distant 

 about 6 mm., having a small area occupied by mesopores ; the apertures 

 immediately adjacent are a little larger than the others, but the difference in 

 size is not conspicuous. 



The characteristic features of this species are the opercula, which are well pre- 

 served in all the specimens seen ; the same feature is also conspicuous in F. oper- 

 culata, but this species may be readily distinguished by the smaller size of the 

 cell apertures, the equally elevated peristomes, the difference in the character 

 of the opercula, and by the mesopores, that species having vesicles between 

 the cell apertures : from F. confertipora it is distinguished by its larger, more 

 distant monticules, the more distant cell apertures, the minute serration of the 

 peristomes, and the much larger mesopores : from F. variapora by the more 

 distant cell apertures, their more nearly uniform size, and the larger mesopores : 

 from F. scrobiculata by the prominent monticules, that species having maculae 

 not elevated above the surface ; the mesopores and cell apertures are very similar 

 in appearance, except that the opercula are rarely present in the cells of the 

 latter species. 



Formation and locality. Hamilton group. West Bloomfield, N. Y. 



FiSTULIPORA PLANA. 



PLATE LVin, FIGS. 19, 22. 



Thallostigma plana. Hall. Trans. Albany Institute, vol. x, p. 187. 1881. 



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



ZoARiUM consisting of thin lamellate expansions, incrusting or free, thickness 

 less than 1 mm. No masses formed by the accretion of successive layers of 



