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REPORT ON THE REEF-CORALS. 93 
d. Gyri of variable depth according to the projection of the lamellate columella, 
from about 3°5 to 6 mm., with a width of from 4°5 to 6°5 mm.; walls rather 
thick; septa with the free border nearly vertical, but more rounded than in the 
previous forms ; paliform lobes scarcely represented except in a few septa from 
about 3 to 5 mm. apart, which become very projecting, so as almost to meet 
from opposite sides; width of ridges from about 4 to 5 mm.; columella not 
abundant, forming but a raised lamella with prolongations from the septa. 
e. Gyri shallow, from about 3 to 4 mm., with a width of from 5 to 7°5 mm.; walls 
thick; septa with the free edge rounded from the edge of the wall to the 
paliform lobe; paliform lobes very distinct, more so than in all the others, 
almost meeting in the centre ; width of ridges above the lobes very variable, 
from 4 to 5°6 mm.; columella not abundant, being a simple lamella more or 
less pressed upon by the paliform lobes, sometimes widening out and distinct 
at the sharp curves of the gyri where the calicinal centres are distinct. 
Between these forms, which are apparently so distinct, there seems to be almost every 
intermediate combination of characters, and the width and depth of the gyri, the thick- 
ness of the wall, the nature of the septa, the development of the paliform lobe, the thick- 
ness of the ridge, and the structure of the columella are seen to be extremely variable and 
irregularly grouped in their combinations. One and the same specimen often presents 
marked differences in structure between its central and its basal parts; and the smaller 
specimens generally agree more closely with the basal than with the central portion of 
the larger ones. 
One special variation in the direction of the gyri may be mentioned as exhibited most 
clearly in one specimen, which may be distinguished as “ form f-” 
J. This form shows gyri which are nearly straight and parallel for distances of from 
4 to 6 cm., and the ridges pass off on each side of a central, nearly straight, 
line almost like the veins in a leaf, curving very slightly to the outer part 
where they become sinuous. These nearly straight ridges are sometimes 
excessively thin, passing gradually into the outer thicker and stronger ones. 
The width of the gyri is from 4 to 8 mm., and the depth from about 4 to 
6 mm. 
The Mzandrina serrata, Mxandrina crassa, and Mxandrina heterogyra, of Milne- 
Edwards and Haime, do not seem to be distinguishable from varieties of this species. 
The Mezandrina heterogyra is clearly identical with the “form f;” the Mexandrina 
erassa corresponds with “form e,” and is represented more or less closely on the outer 
parts of nearly all the varieties of the species; while the Meandrina serrata takes its 
place in the series between “forms a and 6” and “ form e.” 
The species is very close to the Meandrina labyrinthica, which it much resembles 
