96 THE GENUS MONTICULIPORA. 



show at once that the so-called Fistnlipora Canadensis^ Bill., 

 has no claim whatever to be reo^arded as belonfjiiiCT either to 

 Fistnlipora, M'Coy, or to Callopora, Hall (if these generic 

 names are regarded as anything short of identical). On the 

 contrary, it is an unquestionable member of the Favositidcc, 

 with well-marked mural pores, and agreeing in all respects 

 with Favositcs proper, except that the corallum consists of two 

 well-marked groups of corallites of different sizes. The large 

 corallites are oval or rounded, averaging from i-24th to i-28th 

 inch in diameter, and surrounded by from one to three rows of 

 small corallites, which are mostly about half the size of the 

 large tubes, and are more or less angular in shape. The 

 structure of the wall is obliterated in such silicified specimens 

 as I have examined, or is, at any rate, imperfectly preserved ; 

 but it is seen in calcareous examples to be precisely that of 

 Favositcs or Pachypoi'a, the walls being thickened, but the 

 original lines of demarcation between adjoining tubes being 

 mostly recognisable. In no case have I detected any traces 

 of the minute interstitial tubuli figured by Dr Steinmann as 

 present in the fossil which he regards as Fistnlipora Cana- 

 densis, Bill. I cannot, therefore, doubt that the so-called Fis- 

 tnlipora Canadensis, Bill., is either referable to Favositcs itself, 

 or to some closely allied genus ; and the propriety of referring 

 it to Favositcs (in spite of the different sizes of its corallites) is 

 increased by the fact that it passes by seemingly almost insen- 

 sible gradations into an ordinary and unquestionable Favositcs, 

 which has been described as such by Rominger under the 

 name of F. placenta. It should be added, finally, that the 

 radical difference between F. Canadensis, Bill., and all the 

 forms of the genus Fistnlipora, M'Coy, is shown by the fact 

 that long sections of the former (fig. 1 7, b and d) show that the 

 internal structure of the large and small tubes of the corallum 

 is precisely the same, there being no difference whatever in 

 their tabulation. 



Havinof now shown that the structure of the so-called Fistn- 

 lipora Canadensis, Bill., is no element in the problem as to the 



