216 THE NATURALIST IN AUSTRALIA. 
ASCIDIAN-COVERED ROCKS, ROEBUCK BAY, WESTERN AUSTRALIA. 
As matters stand, this rock may conveniently 
serve as a guide-post to that particular spot in 
the Bay, whence, when the tide was low, a con- 
siderable number of the marine forms illustrated or 
referred to in these pages were collected or ob- 
served. 
Although so high up within the tropics, the 
reefs of Roebuck Bay, which render navigation to 
the port of Broome extremely intricate, are not of 
coral, but are stratified replicas of the much-inter- 
rupted friable red sand-stone cliffs that line the shore. 
W. Saville-Kent, Photo, 
Coral grows here, but very sparingly compared with 
a little farther to the north and east. In place of it, certain other marine organisms 
are abundant to an extent that has not been observed by the writer on any other part 
of the Australian coast-line. The zoological group most in evidence among the reefs 
at low tide, at what is known as Entrance Point, close to the ‘“ Rhinoceros Rock” of 
our Chapter heading, is that of the Ascidians. One particular type, referable to the 
genus Colella, literally festoons every ledge and crevice of the much-eroded rocks in 
such a manner that their aspect, as seen from a little distance, presents a remarkable 
resemblance to stalactitic formations. The luxuriant growth of these Colelle, together 
with the peculiar petrological resemblance suggested, will be recognised on a reference 
to the accompanying corner illustration, which is composed of the joined-up replicas of 
several photographs that were taken of contiguous areas. In the lowermost section the 
Ascidians are taken from a nearer point of view, and being more considerably 
