124 Cvicinnati Society of Natural History. 



in others striated; sometimes it is very thin, and at other times 

 strong and thick. The form of tlie cells, as visible on the surface, 

 varies from round to polygonal and in one species, {M. quadratd) 

 the cells are rhombic or square. 



All these, the general form of the corallum, the surface features, 

 and the form and arrangement of the calices, have been considered 

 by some of the recent students of the MonticuUporoids, to be almost 

 valueless. This is especially insisted upon by Dr. Nicholson, who, 

 in both his "Palaeozoic Tabulate Corals," and his "Genus Monti- 

 culipora," asserts time and again that the form of the corallum has 

 no classificatory value. Two quotations must here suffice to show 

 this. He says: " . . . it is quite certain that the mtxe form 

 of the corallum, though affording a useful guide to the collector, is 

 usually of no value whatever in determining the structure and 

 affinities of a given specimen of Monticulipora. As an illustration of 

 this fact, I may mention that among the corals which, from their 

 general form and superficial characters, would unhesitatingly be 

 placed under the well known species M. pet7-opolitana, I find at 

 least three well marked types to be included, which differ so wide- 

 ly from one another in minute structure, that they might well be 

 regarded as at least distinct sub-genera." After stating this, he 

 goes on as follows, to show that sonietitiies, at least, the form of the 

 corallum is of use in determinations. "At the same time certain 

 species, and especially those which have a laminar or frondescent 

 corallum, are very constant in their mode of growth, so that in 

 these cases the form of the corallum is of value in the determina- 

 tion of species ; while the ramose species, however variable, never 

 appear to form crusts on foreign bodies, as some of the massive 

 species occasionally do."* In another place and in another book 

 Dr. Nicholson writes thus: " ... we are obliged to con- 

 clude that the mere external shape of the corallum is a character 

 of no classificatory value. It is not that individual species are 

 specially variable in shape, for many types exhibit a tolerably con- 

 stant form when adult ; but it is the fact that so many structurally 

 diverse species assume the same shape that robs this feature of any 

 special value it might otherwise possess, "f 



Other quotations besides these might be given, but they will 

 be enough to show the small value said to be placed upon external 

 form of the corallum. Before examining into the features which 

 are relied upon by Dr. Nicholson and others, Mr. Ulrich among 



♦Tabulate Corals, p. 273. -j-Genus Monticu., p. 33. 



