126 THE VOYAGE OF H.M.S. CHALLENGER. 
supplementary bases of attachment. The depressions and prominences of the under 
surface small, irregular and numerous. Costal striations distinct, fine and subequal. 
Calicles very irregularly and unevenly placed, often crowded, frequently grouped into 
rather large, nodular masses over the surface, especially on the older parts, owing to the 
development of calicles on the projections. The fossa small and deep, from about 0°75 to 
15mm. indiameter. Septa apparently of three cycles, very close, small and unequal and 
unequally raised, granulated and perforated except at the extreme basal part. Septo- 
costee almost straight at the marginal part of the corallum, and divided into more or less 
irregular, rather large, rounded teeth ; but throughout the rest of the corallum, they are 
iregularly discontinuous, bent, simuous and contorted, rather thin or irregularly swollen, 
thick and tuberculate, unequally tvothed and prominent, more frequently so below 
the ealicles, so that the surface has a rough and very uneven and irregular aspect. 
Columella small, deep down in the fossa, and not conspicuous. The synapticule are 
extremely well developed and abundant, subparallel, and separated by.spaces about equal 
to their own diameter, clearly seen both in transverse and longitudinal section, and fused 
only throughout a thin basal lamina. 
This species shows well the typical structure of the genus, which in its youngest stages 
is closely allied to the genera Agaricia, Leptoseris and Trochoseris, but which with 
growth becomes more clearly related in its adult forms to the genus Pswmmocora. 
It is represented in the collection by a large portion (evidently broken off a large 
specimen), and by two small pieces. 
Locality.—Tahiti. 
2. Domoseris solida, u. sp. (Pl. V. figs. 5-5e). 
Corallum broad, explanate, of a very dense and solid texture, thin, from about 8 to 10 
mm. thick at the central portion, much thinner towards the margin, irregularly shallow-vasi- 
form, with supplementary basal attachments. Under surface very finely striate, with very 
small and irregular depressions and prominences. Calicles very unevenly and irregularly 
placed, often crowded, and frequently grouped into small, nodular masses, due to the 
development of calicles on the projections of the surface. The projections are from 
3 to 7 mm. in height and width, and are very uneven, more or less perpendicular to the 
surface and generally distinctly isolated. The fossa is rather deep and from about 
075 to 1°55 mm. wide. The septa of two or three cycles, small, unequal, close, very 
granulated and solid. The septo-coste in many parts are nearly straight especially 
towards the margin, alternately rather large and small, with an uneven border seldom 
divided into distinct teeth; towards the central parts, and more especially on the pro- 
jections, they are more or less discontinuous, irregularly thickened, bent, sinuous, 
contorted and unevenly prominent, so as to give a rather rough aspect to the projections. 
