152 Cincinnati Society of Natural History. 



the Palaeontology of Ohio. Subsequently, -'^ this authority modified 

 his opinion as to the proper generic name, and substituted J/f ;///<://■- 

 lipora. He was well aware of the variability of the species of this 

 genus, for he saysf in a sort of preface to his descriptions : "Some 

 of the species hereafter described are nearly allied to one another, 

 and in other instances individual specimens may be found which 

 seem to stand midway between two species, and cannot readily or 

 definitely be referred to either. This would give countenance to 

 the belief that future researches might ultimately enable us to unite 

 some of these so called species under one or more highly variable 

 specific types. "J 



The great extent of the group has resulted in various attempts 

 to arrange them into subordinate groups but with little success. 

 The two prominent examples of this division are Dr. H. A. Nichol- 

 son, § and Mr. E. O. Ulrich.|| Their methods and their ideas show 

 a wonderful difference. 



Dr. Nicholson, for example says that from a strictly scientific 

 point of view "the family of the MonticuliporidcB must be regarded 

 as comprismg only the single genus Monticulipora, D'Orb." He then 

 states that he had formerly divided the genus into six sub-genera, 

 and, that while there was no difficulty in framing a generic descrip- 

 tion which would cover all the six, yet three of them were easily 

 separable from the rest by certain well-marked structural features. 

 He then says that "upon the whole, therefore, it may perhaps be 

 the best plan, as a matter of practical cotwenience, to regard these 

 three groups as so many distinct genera, in spite of tlie fact that 

 they have no theoretic claim to such a rank." If this be adopted, 

 the genus Monticulipora is then sub-divided into five sub-genera and 

 three other genera are formed for convenience. 



The other plan, that advocated by Mr. Ulrich, runs to another 

 extreme, and instead of the modest number of three genera and 

 five sub-generic groups, he would have no less than twenty-nine 

 distinct genera and one sub-genus, seventeen of which he coins 

 himself, and hardly two of which does he admit to be more than 

 slightly related. The course which will be pursued in the present 

 paper will be different from either of these. It will follow the 



*More particularly in "The Genus Monticulipora" published in iSSi. 



fPalKon. of OhioJ U, p. 190. 



JThe difficulty of classifying these "half-way" species is felt by all who have col- 

 lected large suites of specimens of variable genera. One of us has kept a box into which 

 the puzzling forms are put as ihev are encountered, and it is wonderful how rapidly they 

 accumulate. In the present paper we shall try to show cause why many of the reputed 

 species should be united under some older and variable species. 



§The Gems Monticulipora, 1871, 00 et. seq. 



ilAmerican Pala-ozoic Bryozoa. Jour. Cin. Soc. Nat. Hist., iS82-'83. Vol. V. VI. 



