50 MADREPORARTA. 
thick, frequently arched and laid across one another at various angles, the whole fused 
together into an irregular network, the meshes of which vary from 4 to 12 mm. across. 
Axial corallites 2 mm. diameter, ] to 2 mm. exsert ; wall rather thick and cylindrical, with a 
flat or slightly rounded apex ; the star consists of six subequal septa of moderate development. 
Radial corallites on the anterior (superior?) surface very unequal, not very crowded; the 
larger ones are tubular, at right angles, with an oblique aperture, from 3 to 4mm. long and 
about 2 mm. diameter, but frequently a little compressed ; a few are longer and proliferous, 
the remainder are less spreading, shorter, tubular, tubo-nariform, and nariform to sub- 
immersed ; the only true immersed corallites on the upper surface occur in the lines of fusion. 
Star imperfect, the directive septa moderately developed, but the others are rudimentary or 
wanting. The radial corallites on the posterior (inferior?) surface are distant, very short, 
chiefly subimmersed or cochleariform. Corallum very porous; surface closely reticulate 
and echinulate, the echinulations often plate-like. Wall of the axial corallites and of the 
elongate radial ones costate above, the cost being echinulate below; wall of the remaining 
radial corallites echinulate in rows. 
Another and a larger specimen in the collection appears to belong to this species and to 
represent a fuller differentiation of the corallum. The specimen is about 96 em. long and 
65 cm. broad, with a very broad base consisting of several stout branches fused together ; the 
branches are 2 em. thick at the base and 1 em, at a distance of about 10 cm. from the apex 
of the corallum. The ultimate divisions form arched branchlets on the anterior surface, 4 to 
5 cm. long in the upper part of the corallum, but shorter and more stunted below. The 
proliferating corallites give rise to short erect branchlets, and the majority of the shorter 
corallites on the anterior surface are nariform or labellate. On the posterior surface the 
corallites are not so short and irregular as in the smaller specimen, and they usually stand 
off at right angles. The majority are very short tubular or subimmersed, others are more 
prominent, up to 2 mm. in length, and a few form sublateral proliferations. 
A similar large fan-shaped specimen has been recently acquired and is 65 em. high. 
Indian Ocean: Mauritius. 
a. Mauritius. Purchased. 93.4. 7.78. (Type.) 
b. ? Waller Coll. 90. 3.29.1. 
c. Indian Ocean ? Purchased. 93. 4. 7. 79. 
30. Madrepora irregularis. (Plate XIV. figs. EH, F.) 
Madrepora alces, Briiggemann (non Dana), Phil. Trans. vol. clxviii. 1879, p. 576. 
Madrepora wrregularis, Brook, Ann, Mag. N. H. 1892, vol. x. p. 458. 
Corallum consisting of alciform plates with marginal, erect, digitiform branchlets, or of 
short, thick, plate-like clusters of incipient branchlets from a narrow base. In the latter 
case the plates are about 8 cm. high, 11 cm. broad, and 3 to 5 em. thick, usually 3 or 4 
radiating from the same base. Under surface uneven, with short appressed corallites. Upper 
surface of the plates composed of very numerous and irregular incipient branchlets with 
immersed and subimmersed corallites between, much as in M. efflorescens, but more irregular. 
