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Cincinnati Society of Natural History. 



by Milne-Edwards and Haime, as was to be expected, in view of the 

 fact that these descriptions relate solely to superficial characters. 

 D'Orbigny's original description of M. mammilla ta (Prodi*, de Paleont., 

 p. 25, 1850), is simply: ' Espece en lame, dont les monticules sont 

 allonges.' This, clearly, might apply to any of the forms I have 

 enumerated (except 6), since all are frondescent, and all have the 

 monticules sometimes or always elongated and compressed. The 

 description given by Milne-Edwards and Haime is much fuller than 

 the above, and is accompanied by figures (Pol. Foss. des Terr. Pal., p. 

 267, PI. xix., fig. L, 1851). It is as follows: 



" Pompier de forme tres-variable, diversement gibbeuse et lobee, en 

 uvueral en frondes larges. epaisses de 6 millimetres environ ; mamelons 

 bien prononces, sauvent un peu allonges, distant d'une fois ou deux 

 leur largeur. Calices polygonaux. peu inegaux, larges d'un cinquieme 

 de millimetre, a peine distincts sur le sommet des mamelous." 



" The above-quoted diagnosis would quite well apply to any one of 

 the four similar-looking forms I have previously enumerated. The 

 figure of the species given by Milne Edwards and Haime represents a 

 lobate sub-massive specimen, and is perhaps more like the form which 

 I have above designated by the letter b than it is like any of the others. 

 It seems tolerably evident, however, that without a microscopical ex- 

 amination of the actual specimens described by Milne Edwards and 

 Haime, it must remain an impossibility to determine accurately which of 

 the above types formed the basis for their description." If it is difficult 

 (I do not think it is impossible) to determine exactl}' what type formed 

 the basis of their identification of M. mammulata, it is certainly much 

 easier to recognize the form which they considered to be D'Orbigny's 

 M. frondosa. The figure given by Milne-Edwards and Haime of the 

 latter species represents an unequivocal specimen of the t3 T pe a (the 

 form Nicholson identifies with M. mammulata^ D'Orb.) Those learned 

 authors were most certainly not in doubt as to which form should bear 

 the name of 31. mammulata, or M. frondosa, since upon the same plate 

 the} r give excellent figures of each, and describe them as distinct. 

 Their figure of 31. mammulata represents a common enough form about 

 Cincinnati, and I have in my collection specimens that are as nearly 

 fac- similes of the specimen figured by them, as it is possible to be, for 

 individual examples of a species which is so variable in its growth 

 (from massive and lobate to distinctly frondescent); while their de- 

 scription of the species applies in all respects, which is more than can 

 be said for any of the other forms in dispute. The species agreeing so 



