THE AUSTRALIAN GREAT BARRIER REEF. 117 



grows in abundance on the rocks at about half-tide mark, and requires considerable force to 

 detach it from the rocks. An elongate shell of this species is illustrated by Plate XIV., Fig. 

 7, of the chromo-lithographic series. A further reference to the habits and characters of the 

 species will be found in the chapter dealing specially with the oyster and oyster fisheries of 

 the Barrier district. 



Three lightships are stationed along the course between Cape Melville and Cape Gren- 

 ville, to guide the passage through the intricate maze of reefs and shoals. The first, known as 

 the Piper Islands Lightship, is a mile or so off Cape Melville. The Claremont Isles Light- 

 ship, the second, occupies a position a little less than ten miles off the mainland, about half- 

 way between the two capes named. The most northern one, Piper Island, is twelve miles 

 due south of Cape Grenville. Both the last-named stations have yielded specimens of interest. 

 From the neighbourhood of the Claremont Lightship, more particularly, varieties of coral which 

 have not been collected elsewhere, have been obtained by the lightship keepers, Mr. and Mrs. 

 Wilson. Among these is Madrcpora ornata, a new species, so named by Mr. Brook, a fragment 

 of which is represented by Plate IX., Fig. 4, of the coloured series. The living tints are, 

 as there shown, a brilliant grass-green, with whitish terminal corallites. It has, so far, been 

 collected only from a depth of two or three fathoms, and with the aid of native divers. From 

 the neighbourhood of the Claremont and also the Piper Lightships, some excellent quantities 

 of sponges belonging to the honeycomb, Hippospongia, and so-called finest Turkish, Euspongia, 

 generic, types have been obtained. This subject will receive attention in another chapter. 



The Forbes, Sir Everard Home, and Sir Charles Hardy, groups, all within a twenty- 

 mile radius of Cape Grenville, are the chief islands of primary-rock formation north of the 

 Flinders' group, in the sectional area now under notice. The largest of these islets, in the Forbes 

 group, scarcely exceeds a mile in diameter, has a hill-summit 340 feet high, and is twenty miles 

 from the mainland. The Sir Charles Hardy group includes three small islands located in the 

 centre of the reef-area, almost due east of Cape Grenville ; their highest point, on the northern 

 islet, is 320 feet. The rock formation of this group is described by Jukes as "siliceous, hard, 

 brittle, and of a brown colour; sometimes putting on the appearance of flinty slate, at others it 

 seemed to be passing into porphyry, containing here and there crystals of red feldspar." In this 

 respect their composition was found by Mr. Jukes to correspond precisely with the rocks of Cape 

 Grenville. Among the smaller rocky islets worthy of notice in the present association, which 

 commonly attract the attention of passengers by the coasting steamers, is one in the immediate 

 neighbourhood of Restoration Island and Cape Direction, about latitude 12° 50" S. Viewed from 

 the north-east, it presents a remarkable resemblance to the semi-submerged head of an Egyptian 

 sphinx, while, by a singular coincidence, the outlying flank of Cape Direction represents, in 

 combination with it, the contour of a perfect pyramid. 



In addition to the two gaps in the Barrier between Capes Melville and Grenville, already 



