52 TABULATE CORALS. 



served otherwise, and whether calcareous or sihcified, it is quite 

 impossible to determine the arrangement of the mural pores, 

 or even to satisfy one's self of their existence ; while microscopic 

 sections afford only a casual help, since they do not show these 

 openings except when and where they happen to coincide with 

 the plane of one of the bounding walls of a corallite. More- 

 over, the arrangement of the pores does not seem to be abso- 

 lutely constant, as has been already pointed out by M'Coy and 

 by Billings ; though, of course, one is here confronted with the 

 difficulty that it is open to any one to assert that all specimens 

 in which the mural pores are not biserial are not specimens of 

 F. Gothlandica, but are referable to some distinct species, even 

 thouo-h their other characters are identical with those of the for- 

 mer type. I can, for instance, quite corroborate the observation 

 of Mr Billings (Joe. czi.) that specimens apparently inseparable 

 from F. Gothlandica in other respects, occur in the Devonian 

 rocks of North America, in which the prismatic faces of the 

 corallites bear sometimes one, sometimes two, and sometimes 

 three rows of corallites, but for the most part two. Such 

 specimens, according to the views of Milne - Edwards and 

 Haime, ought to be separated from F. Gothlandica as a distinct 

 species (/^ Gold/ussi) ; but it appears to me — though it is only 

 with much diffidence that I differ from the views of such justly 

 distinguished authorities — that the mere fact of such great varia- 

 tion in a single specimen is strong proof that the character itself 

 is liable to much variation, and is not, therefore, of specific im- 

 portance. With regard to F. basaltica, Goldf , which resembles 

 F. Gothlandica in general features, but is stated to possess 

 uniserial mural pores, I can express no definite opinion, for I 

 have seen no specimens with this character. Unquestionably, 

 if it were shown that there existed a species of Favosites in 

 other respects like F. Gothlandica, but tmiformly possessino- 

 but a single row of pores on each of the prismatic faces of the 

 corallites, there would be good grounds for reeardino- this as a 

 distinct species ; but the evidence — or want of evidence — on 

 this point, would at present rather lead one to believe that 



