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Show 408 PROF. P. M. DUNCAN O N T H E [June 19, it is perfectly evident that something more than costal structure is implicated, for there are only two rows of processes to one face of the walls of a corallite. The processes stretch across several costae and intercostal spaces, and therefore the true wall adds to the growth as well as the costae. The study of the new species confirms this view of the nature of Phymastraa and that the gemmation is extracalicular. It is proposed to emend the genus as follows:- III. Characters of the Genus Phymastraea, Milne-Edwards Sf Jules Haime, emended. The corallum is compound, massive, and its free surface is convex or plane. The corallites, more or less prismatic, increase by extracalicular gemmation and are joined together by short growths from costae, or from the wall, which are placed with some regularity in vertical series, elsewhere they are separate. A n epitheca exists which may environ the growths. There is a columella, an exotheca, and a well-developed endotheca. The costae may or may not be apparent. IV. Description of the Species hitherto known, Phymastraea valenciennesi and P. profundior. P H Y M A S T R A E A V A L E N C I E N N E S I , Ed. & H. (Hist. Nat. des Corall. vol. ii. p. 500). The corallum is an incrusting subplane form, with a large columella and four more or less complete cycles of septa, the larger being exsert. Tbe nodules are large and warty, and there are two vertical series of them on each face of the more or less prismatic-shaped corallites ; they are enveloped in epitheca. The calices are shallow and pentagonal in outline, and measure from 8 to 10 millim. in diameter. Locality unknown. Specimens in the Michelin Collection at Paris. PHYMASTRAEA PROFUNDIOR, Edwards & Haime. The corallum is incrusting and convex. The calices are polygonal, and are 8 millim. in diameter and are deep. The columella is moderately developed, and there are usually three cycles of septa more or less complete, and sometimes there is one septum of a fourth in each system. The septa are exsert, thickest at the wall, and have a large dentation near the columella. The junction-processes are slender. Locality unknown. Specimens in the Michelin Collection at Paris. The last species is distinguished from the first-named by having deep and smaller calices, a smaller columella, a lower septal number, and slender junctions. As the genus was determined by M M . Milne-Edwards and Jules Haime after the study of these two species, it is clear that the species about to be described is very distinct, for it has costae from which . . . . * the junction-processes arise. |