SUB-GENUS HETEROTRYPA. 109 



occasionally massive ; its surface is covered with well-marked 

 conical monticules, which are sometimes elongated ; and its 

 microscopic structure is entirely different to that of the two 

 preceding types. 



{d) A form which has a frondescent corallum, and a surface 

 covered with prominent elongated monticules, but which has 

 an entirely peculiar microscopic structure, unlike that of any 

 of the forms previously mentioned. This will be subse- 

 quently described under the name of J/. Dazusoni, Nich. 



As before remarked, any one of the above, so far as its 

 external features go, might very well stand for AI. manwmlata, 

 D'Orb. ; and in attempting to decide to which of these this 

 title really belongs, we do not get much help from the descrip- 

 tions given either by D'Orbigny, or 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. inamvmlata (Prodr. 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 /;), 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. i, 

 1851). It is as follows: — 



" Polypier de forme tres-variable, diversement gibbeuse et 

 lobee, en general en frondes larges, epaisses de 6 millimetres 

 environ ; mamelons bien prononces, souvent un peu allonges, 

 distant d'une fois ou deux leur largeur. Calices polygonaux, 

 peu inegaux, larges d'un cinquieme de millimetre, a peine dis- 

 tincts sur le sommet des mamelons." 



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 speci- 

 men, and is perhaps more like the form which I have above 



