168 



THE VOYAGE OF H.M.S. CHALLENGER. 



pedicle. The surface of the wall and costal ridges is smooth, aud covered with a 

 glistening epitheca. The margin of the calicle is deeply and irregularly dentate with 

 sharply angular prominences, corresponding to the primary and secondary costae. The 

 septal arrangement is remarkable for its symmetry and simplicity as occurring in a 

 Flabellum. There are four cycles of septa in six systems, and these are present in every 



Flabellum apertum (Museley). Natural size. 



specimen obtained without any irregularity, the systems being all of the same breadth. 

 The columella is little developed, and composed of scanty outgrowths from the inner 

 ends of the septa. The mean proportion of the axes of the series is about 100 to 137. 



Extreme height of the largest specimen, 20 mm. Length of the longer axis of the 

 calicle, 34 mm. ; of the shorter axis, 23 mm. 



Station 145, off the Prince Edward Islands, South Indian Ocean. 310 fathoms. 

 Six specimens. 



Station 3, off Cape St Vincent, Portugal. 900 fathoms. Two specimens, much 

 decomposed. 



Flabellum japonicum, n. sp. (PI. VII. fig. 3, 3«; PI. XVI. fig. 12). 



The corallum is wedge-shaped, with evenly-curved sides meeting at the gently curved 

 lateral costae. The lateral costae make with one another an angle of about 110°, and the 

 inclination of the faces to one another is about 60°. The surface of the wall is covered 

 with an opaque white epitheca all over, except for a narrow zone close to the calicular 

 margin, which is glistening and polished, and was evidently covered by living tissue in 

 the recent state of the coral, which ceased at the line of commencement of the epitheca. 

 Near its upper border for a wide zone the epitheca is often blackened. The faces of the 

 corallum are evenly curved, and the costae are only just indicated upon them. The 

 lateral costae are sharp but not prominent, and their edges are slightly sinuous. The 

 corallum terminates in a very short bluntly-pointed pedicle. The mouth of the calicle 

 is oval in outline, the margin being slightly excavated opposite each of the half systems. 

 The summits of the shorter axis are somewhat higher than those of the longer, the upper 

 borders of the faces being gently curved. There are six systems and five cycles of septa ; 

 those of the three inferior cycles are incomplete. The septa are of a dull red colour 



