"WBE. ] CANADIAN PALAEOZOIC CORALS. 17 



Yandell and Shumard in the " Contributions to the Geology of 

 Kentucky " refer to Troost's fossil in the following words : — " Favosites 

 hemispherica. — This fossil the most characteristic of the shell-beds, to 

 ■which it is limited, is abundant on the Falls, and is found in masses of a 

 hemispherical figure, which vary from one to ten inches in diameter. It 

 is most commonly calcareous, though sometimes it is siliceous ; " no further 

 information regarding the structure is given. 



Rominger states in his "Fossil Corals of Michigan" that "all the original 

 specimens of Fav. hemisph. kept in Mr. Yandell's collections are identical 

 with Favosites turbinatus of Billings.'' As to most palaeontologists, how- 

 ever, definite descriptions with figures are often the only means available 

 for the study of already described species, and as Billings has evidently 

 given the first description with figures that places beyond doubt the 

 identity of the fossil referred to, it appears best, to the writer at least, in 

 the interests of science, that the name turhinata should be retained for this 

 particular species. 



Favosites nitella, Winchell. 



Favosites nitella,, Winchell. 1866. Rep. Lower Pen. of Michigan, p. 89. 



II nitella, Rominger. 1876. Geol. Sur. Mich., Foss. Corals, p. 32, pi. XI., fig. 4. 

 Favosites placenta, Rominger. 1876. Ibid., p. 32, pi. XI., figs. 1, 2, 3. 



Hall. 1876. Illus. Dev. Foss., pi. XXXIV., figs. 10, 11 and pi. 

 XXXV., figs. 1—12. 

 II II Whiteaves. 1889. Oontr. to Can. Palgeon., vol. I., pt. II., p. 121. 



Corallum small, discoid or at times digitate with a tendency to become 

 nodose or to branch. When discoid the coral expands laterally from a 

 basal initial point of attachment, and rarely exceed 5 inches in diameter 

 and between 1^ inch and 2 inches in height ; the edges are thin, the 

 upper surface flat or undulating, at times nodose, the lower surface gene- 

 rally uneven, covered by a concentrically wrinkled and finely striated 

 epitheca. In gaps in the epitheca of the under surface, at the edges and 

 sometimes on portions of the upper surface the ends of the corallites are 

 closed by opercula. In the digitate forms the corallites incline outward 

 from an imaginary axis and have their outer ends closed by opercula 

 except at the top, or if the coralla or portions of them were prostrate or 

 inclined as they appear to have been at times, opercula are seen on the 

 lower surfaces only. 



Corallites unequal in size, prismatic, with rather thick walls and 

 rounded angles, varying in diameter from -50 to 1 mm. in the same coral- 

 lum. In some specimens or at times in parts only, almost circular 

 corallites about 1 mm. or slightly less in diameter are developed and are 

 seen at varying intervals apart on the surface, the spaces between being 

 2 



