GENERA OF FA VOSITID&. 75 



Favosites clausa, Rominger. 



(PL IV., figs, i- 1 c.) 

 Favosites clausus, Rominger, Fossil Corals of Michigan, p. 36, PL XIV., 1876. 



Spec. Char. Corallum dendroid, of branching or anastomos- 

 ing, cylindrical or oval stems, from two to five lines in diameter, 

 attached by its base, but having its whole free surface covered 

 by the calices, Calices open only in parts of the surface, and 

 especially towards the ends of the branches, but elsewhere 

 closed by flat or convex opercula. Corallites unequal in size, 

 the larger ones being conspicuously circular or oval in shape, 

 and about half a line in diameter, while the smaller ones are 

 more or less angular in form, and vary from a fifth to a third 

 of a line in diameter. Surface commonly marked by raised 

 encircling ridges, which usually have a spiral direction, and are 

 placed parallel with one another at intervals of from half a line 

 to a line or more. These are simply formed by the elevation 

 of the lips of a number of the calices along a given line, and they 

 appear to mark successive stages of growth. Septa obsolete ; 

 tabulae complete, horizontal, or slightly bent, from three to 

 four in the space of one line, sometimes with a few incomplete 

 tabulse interspersed among the others. Mural pores uniserial. 



Obs. This pretty little species may be regarded as a good 

 example of a true Favosites (as distinguished from Pachypora, 

 Lindst), growing in a branching and dendroid form. The 

 inequality of the calices and the markedly circular shape of 

 the larger tubes (PI. IV., fig. i d} are characters in which the 

 species makes a distinct approach to Fistulipora, M'Coy ; but 

 F. Forbesi, E. and H., exhibits the same feature to a less 

 marked extent ; and the presence of mural pores sufficiently 

 separates the present form from the species of the latter genus. 

 It is also separated from Pachypora by the fact that the walls of 

 the corallites show none of that thickening in the neighbour- 

 hood of their mouths which is so characteristic of the latter. 

 The existence of an operculum in the form of a flat or convex 



