408 PKOF. p. M. DUNCAN ON THE [JunC 19, 



it is perfectly evident that something more than costal structure is 

 im|)licatecl, 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 sj)aces, and therefore the true wall adds to the growth 

 as well as the costse. 



The study of the new species confirms this view of the nature of 

 Fhyinastrcea and that the gemmation is extracalicuiar. 



It is proposed to emend the genus as follows : — - 



III. Characters of the Genus Phymastrsea, Milne-Edwards 

 ^ Jules Haime, emended. 



The eorallum is compound, massive, and its free surface is convex 

 or plane. The corallites, more or less prismatic, increase by extra- 

 calicuiar 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. An epitheca exists which 

 may environ the growths. Tiiere is a columella, an exotheca, and a 

 well-developed endotheca. The costie may or may not be apparent. 



IV. Description of the ^i^eeies hitherto known, Phymastrsea 

 valenciennesi and P. profundior. 



Phymastr^ea valenciennesi, Ed. & II. (Hist. Nat. des Corall. 

 vol. ii. p. TjOO). 



The eorallum is an incrusting subplane form, with a large 

 columella and four more or less comjdete cycles of septa, the larger 

 being exsert. The 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 envelojjed 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. 



Phymastr^a profitndior, Edwards & Ilaime. 



The eorallum is incrusting and convex. The calices are polygonal, 

 and are 8 millim. in diameter and are deep. The columella is mode- 

 rately developed, and there are usually three cycles of se])ta 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-jirocesses are slender. 



Locality unknown. Specimens in the ^lichelin C^ollection 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 MM. 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 costaj from wliich 

 the junction-pioce&ses arise. 



