140 THE NATURALIST IN AUSTRALIA. 
of a few inches only. It was observed by the author on one such occasion 
during his residence on Pelsart Island, that the polypes pertaining to the pro- 
jecting extremities of the branching Madrepore, which were thus laid bare 
during the early hours of a winter's morning, were killed by the brief exposure 
to the chilly atmosphere, leaving, after speedy decomposition, the coralla extremities 
bleached perfectly white. Within the moderate depths of from just beneath 
low water mark downwards to as much as ten or fifteen fathoms, the corals 
upon the Abrolhos reefs and within their contained lagoons attain to a 
luxuriance of growth that is not surpassed even upon the Great Barrier of Queens- 
land. Nowhere else, indeed, has the author met with such extensive sheets, as it 
were, of one and the same species spread over continuous areas. This was 
especially notable of certain species of Madrepore or Stag’s Horn Corals. One 
of these, nearly allied to Madrepora hebes, but having a more luxuriant growth form, 
covered acres of the sea bottom in the enclosed lagoon of Pelsart Island. Being of 
a dark purple or purplish brown hue, with the tips and all the growing points brilliant 
mauve or violet, it produced, with the intervening patches of pure white sand, a most 
fascinating scene. In other areas a finer branching species allied to, or identical 
with, Madrepora syringoides, of a dark seal-brown tint with creamy-white tips, and 
growing points, formed equally extensive patches. A cluster of this Madrepora is 
photographically reproduced in the lower figure of Plate XXIII. Seen in bulk, this 
delicately branching white-tipped species was highly suggestive of a free blossoming 
white-flowered heath, the contour of the tubular terminal calicles viewed from a little 
distance wonderfully resembling Epacris blooms. In a third locality a more robust 
light buff-coloured species with heliotrope tips, near Madrepora pulchra, but with 
closely radiating, less divided, branches, represented the dominant type. A double 
or twin corallum of this variety is depicted in the upper half of the Plate last 
quoted. 
A large crateriform or vase-shaped species, ‘ closely resembling Madrepora 
corymbosa, of a golden-brown or brown-pink hue with cream-white edges, undoubtedly 
represents one of the most conspicuous members of the genus indigenous to 
the Abrolhos group. A single corallum of this type is figured in the lower part of 
Plate XXIV. The specimen here delineated measured close upon three feet across. 
Larger matured coralla, however, commonly attain to a diameter of five or six feet 
and upwards, or it may happen that two or three specimens become joined laterally 
to one another, producing an extensive horizontal sheet. The species grows under 
