PHOTOTYPE PLATES NOS. XL/. AND XLIL 63 



of the bank in search ot the smaller algas on which they feed. As the oysters increase 

 in size, the unfortunate whelk becomes proportionately weighed down, and hampered in its move- 

 ments, being finally asphyxiated in the muddy covering of the bank, or condemned to pass 

 the rest of its miserable existence chained to the spot to which, doubtless in pain and 

 anguish, it ultimately dragged its weary " foot." The burden of oysters that one of these 

 small univalve shells can carry, and yet survive, is astonishing. This whelk-shell, with the 

 animal it contains, weighs, on an average, about two ounces, while its load of oysters scale 

 over a pound. Sinbad the Sailor, with his tight-clinging " Old Man of the Sea," was an 

 object of envy in comparison. Examples of Ostira gloiiicrata associated in this same manner 

 with Potamides, have been observed by the author as far north as Cairns, and at many 

 stations further south within the Great Barrier district. Further details of this and various 

 other characteristic forms of this protean and commercially valuable bivalve are included in the 

 special chapter on oysters. 



PLATE X L I I . 



BMRIER REEF SHELLS, 



The photographs reproduced in this plate have been selected with the object of representing 

 a few of the larger and more conspicuous of the rich variety uf shells indigenous to the Barrier 

 district, together with that of illustrating the economical, and decorative uses to which many 

 of the species can be applied. The upper figure depicts a specimen which invites special 

 attention. This is the fiat, irregularly-margined, tray-like object in the foreground that is 

 utilised as a receptacle for the collection of smaller shells. This object is a sponge — not 

 one of soft, delicately-fibrous nature, like our familiar " Companion of the Bath," but composed 

 of a dense mass of minute silicious spicula, so welded together with organic matter as to 

 resemble virgin cork in aspect and texture. This sponge was obtained for the author 

 from what is known as the "old ground" in Torres Strait, by one of the pearl-shell divers. 

 Its systematic position among the vast assemblage of many hundred genera of sponge forms 

 known to naturalists is akin to that of the so-called "Neptune's goblet" (or "Neptune's 

 cup") sponge, Raphyyus Grijfithsi, obtained chiefly from the seas throughout Polynesia, and 

 commonly growing, in the form of an erect cup, or vase, with a distinct supporting stem, to 

 the height of two or three feet. This flattened-out, tray-shaped specimen had no distinct 

 footstalk. It was simply attached by its under surface to the sea-bottom. Superiorly, it is 

 singularly modified so as to form two superimposed smaller trays, which in the illustration 

 are filled with the smallest shells. The addition of an ordinary tripod-stand was alone 

 requisite to convert this remarkable sponge into a highly efficient show-table for marine 

 objects. 



