GENERA OF FA VOSITID^E. 55 



F. favosa, Goldf., must be united with F. Gothlandica, Lam., or 

 at most retained as a distinct variety. 



F. Niagarejisis, Hall, from the Niagara group of North 

 America, seems to be certainly founded upon young speci- 

 mens of F. Gothlandica; and it is possible, as Mr Billings 

 thinks, that Astroceritim parasiticum, Hall, and A. pyriforme, 

 Hall, really belong to the same species. Upon this latter 

 point, however, I can offer no opinion. 



Favosites Winchelli, Rominger {loc. cit), is founded upon 

 forms from the Corniferous and Hamilton groups (Devonian) 

 of North America, which agree with F. Gothlandica in all 

 general features, but have large tubes (one and a half to two 

 lines in diameter), which are occasionally somewhat rounded, 

 while there are only three or four tabulee in the space of two 

 lines. After examining excellently preserved examples from 

 Canada, I am unable to regard this as more than a varietal 

 form of F. Gothlandica. 



Lastly, the name of F. Billingsii has been given by Dr 

 Rominger to a form of Favosites which occurs commonly in the 

 Hamilton group of Ontario, and which grows in large convex 

 discs, varying from one, two, or three inches up to as many 

 feet in diameter. The corallum is attached to some foreign 

 body by a point usually placed in the centre of the base, and 

 the entire lower surface is covered by a striated epitheca. 

 The corallites vary from a line to a line and a half in diameter ; 

 and though of the same essentially prismatic or polygonal form 

 as in typical examples of F. Gothlandica, they are slightly less 

 rectilinear and more irregular in shape and size than in the 

 latter (PI. L, fig. 6). Dr Rominger states that the mural pores 

 are uniserial, and they often are so ; but they are just as 

 commonly arranged in two alternating rows, as in F. Gothlan- 

 dica, and the tabulae resemble those of that species. I have 

 figured a transverse section of this form for comparison with 

 the typical F. Gothlandica, and need only say that as examined 

 in this way the trivial difference in the form of the corallites is 

 much more conspicuous than it is when the calices of the two 



