180 MADREPORARIA. 
a. Var. cespitosa. 
This variety differs little from the form already described excepting in habit. The 
specimens consist of small cespitose clumps 6°5 cm. high and 6 to 8 em. broad; branches 
numerous and very crowded, each similar to one of the branchlets in form A. Immersed 
corallites small and not numerous. 
B. Var. diffusa. 
Corallum spreading arborescent, 24 cm. high and 27 em. broad. Branches curved and 
very spreading, sometimes 18 cm. long and about 1°5 em. thick, gradually tapering. They 
bear numerous branchlets at an acute angle, which vary from elongate proliferous corallites to 
7 cm. in length, all are under | cm. in thickness, and the majority are about 1°5 cm. long. 
Radial corallites nearly all tubular, but the shorter ones are nariform ; a large number are very 
spreading, about 5 mm. long, and bear two or three bud-corallites ;_ the others are shorter 
and less spreading and many are subimmersed, but the truly immersed type is not frequent. 
The star consists of 12 septa, well developed excepting im the short and immersed corallites. 
B. Forma pygmza. 
Colony erect arborescent ; stem 1 em. thick, a little divided. Branchlets 1 to 3 em. 
long, but chiefly under 2 cm., and 3 to 5 mm. thick ; axial corallites not over 2 mm. diameter, 
with a star consisting of 6 septa only. Radial corallites very variable in length and shape ; 
the short ones are nariform, sometimes compressed, and there are various intermediate forms 
through dimidiate to tubiform. The diameter varies from 1 to 2 mm., the length from 
1 to 3 mm.; the longer ones bear bud-corallites. The wall varies considerably in thickness, 
often rather thin and only showing a thickness proportionate to that of other varieties in 
the tubular corallites. Immersed corallites practically absent, their place being taken, 
on the stems and branches, by appressed nariform or tubular ones. Surface of the 
ccenenchyma as in the other varieties, but the wall of the corallites near the apex of the colony 
is substriate. 
This is the form recorded by Quelch, and all the ‘ Challenger’ specimens belong to it. It 
differs chiefly in the more slender branchlets, the much smaller corallites, and the absence 
of immersed corallites. 
C. Forma dumosa. (Plate XVI. fig. A.) 
Habit similar to that of var. pygmea, but more bushy, and the twigs are more acuminate. 
The colony may be 21 cm. high and 20 cm. broad, the upper 12 cm. consisting of a new 
incrustation over a dead colony. Near the base the branchlets often consist of a thick 
tapering axial corallite, with scarcely open buds to within 9 or 6 mm. of the apex only; 
diameter at the apex 1‘6 mm., diameter 9 mm. below that point (where the last bud is 
situated) 2°3 mm.; margin rounded, aperture scarcely recognizable. Nearer the apex “of the 
colony the axial corallites bear buds to within 2 or 3 mm. of the margin, which is then not so 
