54 TABULATE CORALS. 



inner surfaces of the walls of the corallites, arranged in vertical 

 series. In other cases, the septa have the form of delicate but 

 unequally distributed spinules, which roughen the interior of 

 the tubes. Finally, there are specimens in which the septa 

 are so far developed as to assume the form of regular radiating 

 spines (PL I., fig. 5), which may extend nearly to the centre of 

 the visceral chamber, and are usually from twelve to fifteen in 

 number. It is upon examples of this kind that Professor Hall 

 founded his genus Astrocerium; but there can be no doubt that 

 these forms with spiniform septa are simply a varietal condi- 

 tion of this and other species of Favositcs. 



Before leaving this species, it may be as well to make a few 

 remarks upon some of the forms which I have included under 

 it. As has been previously said, F. Gothlandica was regarded 

 by Milne- Edwards and Haime as essentially a Silurian species, 

 and the corresponding Devonian forms were separated by them 

 under the name of F. Goldfiissi. This latter species Is sep- 

 arated by its authors from F. Gothlandica simply upon the 

 ofround that its corallites are said to be larofer, and that the 

 mural pores are more closely set than in the Silurian form. 

 The size of the tubes (one and a half line) is, however, fre- 

 quently exceeded by typical Upper Silurian examples of F. 

 Gothlandica, and, under any circumstances, cannot be regarded 

 as a character of the smallest specific value, while the mural 

 pores exhibit at least an equal variability. I am therefore 

 quite unable to accept the separation of F. Gold/icssi from 

 F. Gothlandica. 



F. favosa of Goldfuss has at first sight more claims for 

 separation from F. Gothlandica, the strong convexity of the 

 tabulae (which led Milne-Edwards and Haime to speak of their 

 possessing a small central columellar eminence) being a very 

 marked feature in some specimens, which otherwise entirely 

 agree with the latter form. The arching of the tabulse is, how- 

 ever, very variable, and one and the same specimen may 

 exhibit both convex and flat tabulae ; so that in the absence 

 of any distinctive character of a more constant nature, I think 



