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Show 1883.] MADREPORARIAN GENUS PHYMASTRAA. 407 sequently the diagnosis of the genus was given in their work entitled • Recherches sur la Structure et la Classification des Polypiers recents et fossiles ;' and finally in their great work, the ' Histoire naturelle des Coralliaires,' tome ii. p. 499 (1857). The generic diagnosis of 1857 does not correspond in a very important point with that published in 1848; and there is no doubt that the last diagnosis is erroneous. The great French zoophytolo-gists described two species of the genus Phymastraa in their last-mentioned work, having noticed them fully in their previous one. Unfortunately the geographical positions of the two species are not ' known. Probably they are from the Eastern seas. II. The Generic Diagnoses of Phymastraea1 given in 1848 and 1857. The generic diagnosis given by M M . Milne-Edwards and Jules Haime in 1848 is as follows :- " Corallum in a convex or plane mass. Corallites prismatic and enveloped from the base to the summit by a thin epitheca without a trace of costae. Corallites close, not joined by thin walls but, at certain distances, by large wart-like projections, so that there are considerable spaces between the walls of contiguous corallites. The gemmation is extracalicular and subapical. The walls are thick ; the calices are subpolygonal, and their margins are free; the columella is spongy in texture and well developed ; and the septa are well developed, slightly exsert, and strongly toothed, especially near the columella." The generic diagnosis published in 1857 contains the same characters, but there is an alteration regarding the method of increase of the corallum in the nature of the gemmation. This is stated to be calicular and submarginal. Fortunately the drawings and descriptions of the species of Phymastraa which were published along with the first diagnosis of the genus will satisfy any student of the Madreporaria that the gemmation is extracalicular, and from the wall beyond the edge of the calices. The second diagnosis is therefore incorrect; and this opinion is maintained after the examination of the third and hitherto unpublished species. In noticing the remarkable method of the junction of the corallites of Phfinastraa, M M . Milne-Edwards and Jules Haime state that the genus has great affinities with others of the Astraeidae, and that this method is characteristic. It is necessary to draw attention to the statement that the corallites are invested with a thin epitheca and that there is no trace of costae. It is evident, moreover, that M M . Milne-Edwards and Jules Haime considered the junction-processes to be invested with epitheca, but to consist of an almost compact structure. These processes " se soudent fortement a la muraille dun polypierite voisin." In the delineation of the species Phymastraa valenciennesi, Ed. & IL, on pl. ix. figs. 3 & 3 a (Ann. des Sciences Nat. 3 serie, t. x., Zool.), 1 <pvpa, a thing that grows upon the body. |