169 THE VOYAGE OF H.M.S. CHALLENGER. 
generally about 2°5 mm. wide, sometimes more, very short and thick, with very porous 
edges, and with a very distinct star of twelve septa. In many apical cups small or rudi- 
mentary septa of athird cycle are present, and in a few cups of larger size they are large 
and well developed. The lateral calicles are very unequal and variable, generally about 
1°5 mm. wide, immersed and rather widely placed on the under surface and over a large 
part of the upper surface ; often slightly prominent on one side, forming very short, open, 
round-nariform cups, while not infrequently they are crowded, and, by the thickening 
and upgrowth of the under side, shortly verruciform. The stars are very distinct, of 
twelve unequal septa; and in those calicles which are not verruciform, two opposite septa 
of the first cycle become decidedly and strongly-exsert. The ccenenchyma is porous in 
the younger parts, becoming closely reticulate and dense below; the surface very roughly 
and closely echinulate, and strongly striated on the under sides of the calicles. 
A single specimen of this species was obtained. It has grown prostrate in one 
direction to a length of about 26 cm., branching laterally and so closely that the branches 
are broadly coalescent at the point of origin. Many parts of it are dead, and more or 
less incrusted by fresh growth. Its peculiar characters separate it widely from all other 
known species of the genus. 
Locality. —Banda. 
34. Madrepora aculeus, Dana. 
Madrepora aculeus, Dana, Zoophytes, p. 450, pl. xxxii. fig. 6. 
A small, dead, and somewhat incrusted fragment of a corallum has been doubtfully re- 
ferred to this species. It differs from Dana’s figure chiefly in the nature of the branchlets, 
which are here shorter and furcate, sometimes divided into three or four, with a thick base 
from about 7 to9 mm. in diameter. In other essential characters it agrees with the species. 
Locality. 
Samboangan, Philippines. 
35. Madrepora angulata, n. sp. (Pl. IX. figs. 5—5a). 
Corallum arborescent and rather sparsely branched, somewhat prostrate ; the main 
stem elongated, subterete, or slightly and irregularly compressed, or twisted and acutely 
angular, of nearly uniform size throughout, from about 6 to 8 mm. wide, somewhat wider 
at its upper part where the main branches originate. The branches and chief branchlets 
are but slightly smaller than the main stem, rather short and angular, not coalescent ; 
the young branchlets much smaller and tapering ; they develop chiefly on opposite sides 
of the stem at an angle of about 50°, but many are found placed quite irregularly. 
Apical calicles not large, scarcely prominent, about 2 mm. wide, sometimes more, with 
thin edges which are not porous; star distinct, of six large, unequal septa, and six smal] 
