162 THE VOYAGE OF H.M.S. CHALLENGER. 
Station 308, off Tom Bay. 175 fathoms. 
Station 311. 245 fathoms. 
Desmophyllum eburneum, n. sp. (PL VI. figs. 1, 1a, 10). 
Only imperfect specimens of this species were obtained. The corallum is of a pure 
white. It is elongate conical in form, slightly compressed, with a long cylindrical pedicle 
which expands slightly at the broad base of attachment. The outer surface of the 
corallum is remarkably smooth and polished, and glistens like polished ivory. The 
primary, and in some specimens also the secondary costs appear on the surface, where the 
corallum begins to expand, as slightly prominent ridges, here and there roughened by 
slight indentations. The development of the costz varies much in different specimens, 
as also the amount of exsertion of the septa. The primary septa are prominently exsert 
and sometimes unequally so, and some are bent over outwards beyond the margin of the 
calicle. In some specimens the secondary coste are as far exsert as the primary ; the 
tertiaries are only slightly exsert. There are six systems of septa and four complete 
eycles. The septa are straight and thin, and are covered on their faces with sparsely 
scattered, small-pointed granules. Only the primary and secondary septa extend to meet 
one another laterally around the centre of the calicle, where their perpendicular margins 
surround a deep but narrow fossa. 
Judging from the broken specimens, the height of the full-grown calicles is probably 
about 35 mm. Extreme breadth of a perfect calicle, 21 mm. 
Station 306. Off Middle Island, Patagonia. 345 fathoms, 
Desmophyllum cailleti, Duch. and Mich. 
Desmophyllum cailleti, Duch, and Mich., Supp. Mém. Coral, 1874. 
A single dead and partly decayed specimen obtained off the Virgin Islands appears 
referable to this species; if so, it is large, measuring 30 mm. in height, and 20 in 
diameter of the calicle. 
Station 24. Off Culebra Island, Danish West Indies. 390 fathoms. 
Flabellum, Lesson. 
Notes ON THE STRUCTURE OF THE Sort Parts OF SPECIES OF THE Genus Plabellum. 
When a specimen of a Flabellum hardened in absolute alchohol is decalcified, no trace 
of any external layer of soft tissue covering the outer surface of the wall remains. The 
living tissues in FVabellum are confined to the interior of the calicle and the immediate 
outer edge of its margin. The decalcified mass of soft tissue which occupied the interior 
of the calicle, consists of twelve wedge-shaped lobes connected together at their narrowest 
ends by means of the central stomach of the animal. The interior of each of the lobes 
