3° 



CHAPTER II. 



THE GENERAL AND COMPARATIVE STRUCTURE OF 

 MONTICULIPORA. 



The genus Moiiticulipora, D'Orb., using this name in its wide 

 sense, comprises a large number of Palaeozoic fossils, which 

 range from the Lower Silurian to the Carboniferous, inclusive. 

 They attain their maximum in point of development, both as 

 regards species and individuals, towards the middle or end of 

 the Lower Silurian period, being much less abundant in the 

 Upper Silurian, and still less numerous in the Devonian and 

 Carboniferous deposits. Species of the genus have been stated 

 to occur in the Permian rocks, but I am not aware that this 

 observation rests upon microscopic examination. 



As regards its generic^ characters, Monticulipora, D'Orb., 

 may be defined as including forms in which the corallum is 

 composed of numerous closely approximated tubular corallites, 

 the walls of which are never absolutely amalgamated with one 

 another, though sometimes seemingly so. Walls of the coral- 

 lites imperforate. Septa entirely wanting. Tabulae always 

 present in greater or less number, though sometimes nearly 



1 In the following definition, the name of Monttculipora is used in its widest 

 sense, as embracing all the types known to palaeontologists as Mo7iticulipora, Fis- 

 tulipora, Dekayta, and Constellaria. As will be afterwards shown, these types agree 

 with one another so closely that they can be readily included under a common 

 definition ; and they therefore form a natural genus. At the same time, it is very 

 inconvenient, as a matter of practice, to include many sub-genera under a single 

 genus; and I shall therefore treat Fisfitlipora, M'Coy, Constellaria, Hall, and 

 Dckayia, E. and H., as if they were so many distinct genera, though their distinc- 

 tive structural features would not seem to be of sufficient importance to warrant 

 our regarding them in actual fact as more than mere sub-genera di Mfl7iiiciilipora. 



