viii PREFACE. 



admitted that has not been subjected to a careful microsco- 

 pic examination, and the minute structure is always figured 

 as adequately and fully as considerations of space and cost will 

 allow. 



For the same reasons, I have not troubled myself greatly 

 about matters concerning the bibliography and synonymy of 

 the genus, chiefly because it will be impossible to take up this 

 part of the subject with much satisfaction or utility until the 

 actual specimens originally examined and described by the 

 earlier workers in this department shall have been investigated 

 by modern methods, and thus, for the first time, clearly and 

 unmistakably identified. It is quite possible, therefore, that 

 when the investigation I have just alluded to has been carried 

 out, and its results published, it may be found that some of the 

 forms which I have here identified with previously described 

 species are in reality distinct from these.^ This source of 

 error, in the present state of our knowledge, seems to be 

 absolutely unavoidable, even by the most careful observer ; 

 and it must be sufficient for me that my descriptions and 



^ As an example of this, we may take such a form as Monticnlipora vicwuimlata, 

 D'Orb., commonly cjuoted as one of the characteristic fossils of the Cincinnati Group 

 of Ohio. In determining what species M. Jiiaiiunitlata, D'Orb., really is, we do not 

 o-et any help from D'Orbigny himself, as his description is utterly worthless for pur- 

 poses of identification. We have to fall back, therefore, upon the fuller description 

 and the excellent figures given by Milne-Edwards and Haime of what they believed 

 to be M. inanDiuiIafa, D'Orb. (Polypiers fossiles). It so happens, however, that the 

 Cincinnati Group of Ohio contains three Monticuliporoids, any one of which might 

 be identified with the M. viammulata of Edwards and Haime, so far as form and 

 external characters go, but which differ widely in their microscopic structure. Now, 

 without microscopically examining the actual specimens upon which Edwards 

 and Haime founded their description, it would be impossible to determine which 

 of these superficially similar forms is the actual M. iiiammulata of the French 

 observers ; and one has therefore to choose between the total rejection of this 

 long-current species or the arbitrary selection of any one of these three as really 

 the form originally described. I have followed the latter course, but I freely admit 

 that my selection has been an arbitrary one ; and the form which I call M. viammu- 

 lata, D'Orb., may possibly be shown ultimately not to be really the species which 

 the authors of the ' Poh'liiers fossiles' described under this name. 



