40 
small, often single, and at the same level over a considerahle extent of the 
coralliim, and having the appearance, under a low iiowcr, of strings of widely- 
separated semi-transparent heads. At times the wall, above or below, usnally 
above, is to some extent thickened, and it may happen that at times several 
swellings follow one another rapidly, hut without becoming confluent. In 
/S'. ias})icmicnsis and S. ocata, when moniliform swellings do occur in their 
axial regions, they are much on the same plan as the above. On examining 
the peripheral region of the several species we fmd a much greater diversity 
of structure existing. In S. ocata the annulations of the tubes, on the latter 
passing from the axial to the peripheral zone, gradually lose their ellijd.ical 
form and become oval-pyriform, approaching nearer to one another as the 
surface of the coralliim is approached. Although becoming ultimately close 
set and forming a continuous line, with great regularity, like a series of waves, 
the swellings never thoroughly lose their pyriform outline, and, in con- 
sequence, do not become confluent. The moniliform swellings of S. australis, 
N. & E.,^ are similar, hut those of the axial region of this species and S. 
Leichhardt i I am not acquainted with. Near the surface of the coralliim 
many of the swellings in S. ovala are quite cyepiform (PI, VI, Eig. 8), and 
appear to have their larger ends reversed. In 8. Leichhardti, N. & E.,^ the 
swellings have quite lost the moniliform or annular outline, and have become 
perfectly confluent, except just at the periphery of the coralliim, where the 
characteristic form may still he recognised. The aspect usually presented in 
sections of this species is that of a series of thickened walls, gradually 
increasing in width upwards, with uniform margins, or at any rate only 
widely serpentine. In 8 . tasmauiensis the moniliform swellings are, when 
single, generally elliptical, hut sometimes caepiform, hut, as a rule, the whole 
peripheral line in this species becomes thickened into a dense mass of scleren- 
chyiiia (El. VII, Eig. 9), hut in which the laminar structure is still visible. 
Lastly, in 8. critiita the moniliform swellings appear, at the termination of 
growth periods, to retain the same general character as in the axial region, 
simply becoming closer together, but still possessing the same fusiform 
appearance. One very characteristic feature, however, in these bodies is their 
much more slender outline than in any of the others. 
The interstitial surface of the coralliim and the angles between the 
eorallites are more frequently than not occupied by small blunt spines which 
project more or less above the general surface. These have been termed by 
1 Aim. Mag. Nat. Hist., 18S6‘, XVII, t. 3, f. 6. 
* Ami. Mag. Nat. Hist., 188G, XVII, t. 3, f. 8. 
