348 PERCY SLADEN TRUST EXPEDITION. 
The terminal branches are oval in section, the diameters are about 3 mm. x 2°75 mm. 
Specimens were sent to me from Coetivy, Praslin Reef, Egmont, and Farquhar Atoll. 
In all cases they were obtained in shallow water. 
6. Distichopora profunda, sp.n. (Plate 44. figs. 4, 5, 6, 7.) 
Off Salomon Atoll, Chagos Archipelago, 120-150 fms. Two specimens, one “ dead.” 
As far as can be ascertained from one of the small colonies obtained, the growth is 
flabellate, the branches being very stout, obtuse, and flattened in the plane of the 
flabellum. The thickest branch is 10 mm. x 4 mm. in diameter, while the base of the 
main stem is 7 X 4mm. The colony is not old enough for it to be ascertained whether 
the method of growth is dichotomous or anastomosing. ‘The colour is brownish white, 
the surface is very rugose, recalling the structure of Sporadopora dichotoma, but as the 
pits and furrows of the ccenenchym-canals are much deeper and larger they can be 
easily seen without magnification. ‘The pores are confined chiefly to the lateral sides of 
the branches, where there is generally a double row of gastropores bordered by a single 
row of dactylopores on each side (‘4.‘2 mm. in diam.). The latter are usually horseshoe- 
shaped, the outer edge slightly raised above the surface of the coral, the “open” end of 
the horseshoe being turned towards the row of gastropores (figs. 5 & 6). 
The dactylozooid is attached to the outer side of its pore and can be completely 
retracted within it, the free end pointing inwards—that is to say, towards the gastropores. 
Sometimes the line of pores is continued on to either of the surfaces of the coral ; there 
may also occasionally be a few isolated pores (fig. 4), a gastropore with one or more 
dactylopores near it upon the surface. The gastropores vary in size ; the larger ones are 
05 mm. in diameter. In D. violacea they are rarely more than 0°3 mm. in diameter. 
The arrangement of the gastropore-cavities is fan-shaped, as in D. violacea. 'The long 
gastrostyle is brush-like at the tip. One important feature of this species is that 
tabulze are common in the gastropores (fig. 7). The tabula do not occur in very young 
(that is to say, shallow) gastropores, but more than one may be present in the older pores. 
Moseley only describes tabule in Sporadopora aud Pliobothrus. We have found tabulee 
also in Spinipora echinata (p. 353), another species which has very deep gastropores, and 
on re-examining Déistichopora violacea we have found that they do occur in the older 
gastropores of that species. In many of these there are several incomplete tabule—that 
is to say, excrescences—from the wall of the pore that may or may not reach the 
gastrostyle. These incipient tabula sometimes are seen in D. profunda (fig. 4). 
In his discussion of the pedigree of the Stylasterina, Moseley (5) expressed the opinion 
that Sporadopora is the most archaic genus, and that Distichopora is probably derived 
from some form allied to Hrrina. One of the results of our investigations derived from 
the study of the two new species Sporadopora providentiea and Distichopora profunda is 
to show that the two genera are much more closely related than Moseley believed. 
It must be observed, however, that there is a striking difference between the male 
gonangium of Sporadopora and that of Distichopora. In the former there is a 
well-marked elongated cylindrical spadix, in the latter there is none (¢f Moseley, pl. 3., 
and Hickson, 3. pl. 30. fig. 15). 
