64 TABULATE CORALS. 



corallites, and biserial or triserial mural pores; and the only 

 question, to my mind, is as to whether it should be regarded 

 as a variety of this, or as a distinct species. That it belongs 

 to the same type-form cannot be questioned, and I formerly 

 referred it unconditionally to F. Forbesi, E. and H., which was 

 to all practical intents and purposes the course followed by Mr 

 Billings, with this difference, that he regarded F. Forbesi as 

 a mere synonym of F. basaltica, and therefore employed the 

 latter name. Having now made a careful microscopic exam- 

 ination by means of thin sections of both the present form and 

 of typical examples of F. Forbesi, E. and H., from the Upper 

 Silurian, I still think that the two are substantially identical ; 

 but the former presents so many peculiarities, that it may 

 reasonably stand as a distinct variety. For this I have 

 adopted the specific name given to it by Dr Rominger (loc. cit.\ 

 who describes it as a distinct species a view for which I am 

 inclined to think there is as yet hardly sufficient evidence. 



In general shape, the corallum of the present form only 

 differs from that of the typical F. Forbesi, E. and H., in the 

 general predominance of a cylindrical or clavate, rather than a 

 spheroidal figure. I have given a drawing of the youngest 

 and smallest specimen I have seen (PI. III., fig. 2), which gives 

 a very good idea of the general form of the corallum, though 

 adult examples may be six inches or more in length. The 

 characters of the corallites are, also, those distinctive of F. 

 Forbesi (PI. III., fig. 2 a), there being a very marked inequality 

 in the sizes of the tubes, and the larger ones being more or less 

 strikingly cylindrical, rather than strictly prismatic. The large 

 tubes, however, are of comparatively great size, and are com- 

 paratively numerous, while the small tubes are reduced pro- 

 portionately both in size and numbers the condition of things 

 thus rather resembling what we see in the yozmg of the typical 

 Upper Silurian F. Forbesi than in the adult of the same. In 

 calcareous examples from the Hamilton formation of Canada 

 (PI. III., fig. 2 b}, the largest tubes are not so numerous, 

 while the small tubes are increased both in numbers and in 



