236 NEW YORK STATE MUSEUM 



the middle Coeymans gave as greatest diameter of the coralhtes 

 1.25mm, the average width was imm. It gave in one section 12 

 tabulae in lomm; in another 18 in 15mm, averaging i^ to imm. 

 The wall in both specirnens is always twice as thick as the tabulae. 

 The majority of tabulae on the Coeymans specimen are very 

 regularly concave with a concavity of from one third to one fifth the 

 diameter of the corallite. The specimen from the Favosites bed 

 shows most of the tabulae flat with only a few concave. A few 

 tabulae on both specimens are placed obliquely to the walls. There 

 were faint indications in both specimens when placed in weak acid 

 for a short time of from one to two rows of pores on the sides of 

 the cells, usually located about halfway between the tabulae. 



Comparison of Favosites niagarensis and F. helderhergiae 



F.niagarensis F. h el d e r b e r gi ae^ 

 Average width of cells i . 3mm i . 5mm 



Usual number of tabulae 



in lomm 7-9 12 



Extreme number of tab- 

 ulae in lomm 4, 10-12 10, 15 



Corallum Lenticular or Spheric 



hemispheric 



Professor Hall says^ that ''F. helderhergiae differs from 

 F. niagarensis (which it resembles in the size of its cells) in 

 having more numerous diaphragms and in the mural pores being on 

 the lateral faces instead of at the angle of the cells." His figures of 

 F.niagarensis, however,"^ show the pores on the lateral faces 

 of the cells and not at the angles. This would leave no difference 

 between the two species except the number of tabulae. The cells of 

 a specimen in the Columbia University collection from the Niagara 

 limestone, locality not given, average about 1.3mm in diameter; it 

 has from 13 to 16 tabulae in lomm, while the one to two rows of 



^Measurement taken from Hall's figures, Pal. N. Y. 2:125, pi. 34a (bis), 

 fig.4a-i. 

 ^Pal. N. Y. 6:8. 

 ^Pal. N. Y. V.2, pl.34a. 



