56 THE VOYAGE OF H.M.S. CHALLENGER. 
5. Stylophora cellulosa, n. sp. (Pl. I. figs. 2-2c). 
Corallum forming, large more or Jess rounded clumps, the branches of which are 
elongated, much compressed or angular, and divided throughout into rather broad sub- 
palmate lobes ; these branches are from 1°5 to 4 em. wide and about 7 to 10 mm. thick 
ut their upper part, beg often subterete at their base ; the lobe-like branchlets are 
short, broad, rounded or angular, often swollen at their apex, and subdivide rapidly and 
longitudinally into smaller lobes, apparent as incipient lateral crests, in a plane at right 
angles to their width. Calicles very crowded towards the apical parts, where they are 
from 1 to 1°5 mm. in diameter, polygonal and deep, with generally thin, but unequal 
interspaces, which are of an open cellular structure; towards the basal parts they are 
circular, smaller and shallower, less crowded but not distant, and separated by dense 
interspaces ; throughout the corallum the calicles are even with the surface and generally 
fringed by small spinules, those on the distal margin being often rather more elongated 
than those on the proximal, but the upper edge is neither prominent, arched nor vaulted. 
Septa six, well developed, those in the extreme distal calicles being very conspicuous, 
broad and very thin, meeting quite at the centre, the interseptal chambers being very 
wide and deep; those in the proximal calicles beimg much less conspicuous, distinet only 
at the bottom of the fossa, much thickened and not exsert, coalescing with the columella 
so as to form a thick central mass which is concave above, and which, nearly filling up 
the bottom of the cup, renders the interseptal chambers small and narrow, though quite 
deep. The styliform prolongation of the columella generally absent, except in the 
extreme apical calicles, where it is represented by a very small, short pointed style placed 
above the point of union of the thin septa. Coenenchyma very cellular and light 
throughout the apical parts, but becoming dense at the peripheral parts of the basal 
portions ; surface covered with fine and short spinules. 
This species is extremely close to the fossil species Stylophora raristellata, from 
which it differs in that the calicles are closer and are not margined by a solid ring-like 
edge. The styhform columella also is much less developed than in Stylophora 
raristellata. From the Stylophora danx, to which it is closely allied, it may be 
distinguished by its less dense ccenenchyma, its narrower branches, its even calicles, 
which are neither distinctly raised at the margin nor furnished with a projecting upper 
lip, its much shorter, more thickened, and less developed septa, which throughout the 
greater part of the corallum, and especially at the basal portion, are distinct only at the 
bottom of the calicle, and do not take the form of the vertical plates characteristic of the 
older calicles of Stylophora danx. The styliform columella is also absent, except in the 
extreme apical calicle, the centre being occupied by a broad concave mass, with which 
the septa are united, while in the Stylophora danx a distinct styliform columella is 
