GENERA OF FA VOSITID^E. 141 



vesicular varies in different species of the genus ; and the con- 

 dition of these structures is in any case very different to that 

 which obtains in Favosites {Evimonsia) heinispherica, Yand. and 

 Shum., where the tabulae are mostly actually " incomplete," and 

 do not become united with contiguous plates. The tabulae 

 often carry on their upper surface vertically-directed spinules, 

 which may be regarded as a continuation towards the centre of 

 the marginal septa. These latter are in the form of vertical 

 striae, or ridges, or rows of tubercles ; and their number varies 

 from twenty-five to fifty. 



It will be evident from the above description that Michelinia 

 is a true Favositoid coral, very nearly allied to Favosites itself, 

 near which it has been almost uniformly placed by palaeontolo- 

 gists. It does not, in fact, differ from Favosites proper in any 

 characters except that the tabulae usually subdivide and become 

 more or less united among themselves, while the septa are 

 more numerous, and are not spiniform, and the mural pores 

 are irregularly distributed. Of these peculiarities the subvesi- 

 cular character of the tabulae is the only one of generic import- 

 ance, and even this is not equally noticeable in all the species. 

 The occasional presence (as in M. favosa, Goldf.) of radiciform 

 prolongations from the lower surface — apart from the fact of 

 the total absence of these structures in most of the species — 

 cannot, in my opinion, be regarded as sufficient to overbalance 

 the many and weighty resemblances between this genus and 

 Favosites. I am therefore altogether unable to agree with my 

 friend Dr Lindstrom in thinking that Michelinia should be 

 removed from the Favositidce and placed in the family of the 

 CystiphyllidcE (On the Affinities of the Antkozoa Tabulata^ 

 Ann. and Mag. Nat. Hist, sen 4, vol. xviii. p. 12). 



I shall in the meanwhile, for reasons to be stated imme- 

 diately, retain Plettrodictyum, Goldf, and C/i07iostegites, E. 

 and H. (= HaimcophylliLm, Bill.), as generically distinct from 

 Michelinia, though I think that the first of these, at any rate, 

 will ultimately have to be united with the present genus. If 

 this course be followed, then the genus Michelinia is only 



