GENERA OF FA VOSITID.E. 69 



tion is warranted by the published description of the original 

 author, since this is obviously all of which other observers can, 

 as a rule, avail themselves. Taking this view of the question, 

 I quote the entire description of the species given by Yandell 

 and Shumard (Contrib. to the Geol. of Kentucky, p. 7) : — 



'' 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." 



Passing over the obvious fact that the above description — 

 unaccompanied by any figure — is wholly worthless as char- 

 acterising any species of Favosiies, and that its vagueness 

 would have altogether justified Milne- Edwards and Haime 

 in giving a new specific title to the form which they were 

 describing, it may be simply remarked that the only two 

 tangible points alluded to by Yandell and Shumard are the 

 shape and the size of the corallum ; and in both these points 

 their description agrees with the Emmonsia hemispherica of 

 Edwards and Haime, and differs from the description of F. 

 turbinata given by Billings. The form of F. turbinata, Bil- 

 lings, though not absolutely uniform, is almost always that 

 of a bent cone, rendering the name ttirbinata a very apt 

 one ; while of the many examples I have seen, none could 

 be properly said to be "hemispherical," and none exceeds 

 some five or six inches in diameter. On the other hand, 

 Emmonsia hemispherica, E. and H., is typically "hemispheri- 

 cal" in form, and is often eight or ten inches in diameter 

 (Billings gives two or three feet as the maximum diameter 

 of specimens observed by him). Upon the whole, then, I 

 cannot but conclude that the names of F. hemispherica, 

 E. and H., and F. hirbinata, Bill., ought to be retained 

 for the forms described by their respective authors under 

 these titles, and that these names should not be invalidated 

 by any evidence which is not based exclusively upon, or 

 directly supported by, published descriptions or figttrcs of 



