PEARLS AND PEARL-OYSTERS. 209 
of this plan, additional instalments for the Shark’s Bay grounds have, as a matter of 
‘fact, been recently transported to the Dirk Hartog cultivation grounds, under the able 
management of Mr. John Brockman, the Shark’s Bay Pearl Shell Fishery inspector. 
Some attention may now be given to that second and smaller species of 
Mother-of-Pearl shell which is indigenous to Shark’s Bay and which in former years 
constituted a by no means unimportant fishery. This is the Meleagrina imbricata of 
conchologists, known to the trade as Shark’s Bay shell, since, though occurring in more 
or less abundance throughout almost the entire northern moiety of the Australian 
coast-line, it is only in Shark’s Bay, Western Australia, that it grows in such 
abundance as to constitute a systematic fishery. Considerable difficulty has been 
experienced in precisely fixing the technical title of this shell. The above name was 
originally awarded to it by Reeve, but he at the same time conferred upon other 
examples from the Australian Coast, which are evidently young or local variations 
only of the same species, many additional titles, including notably those of irradians, 
lacunata and fimbriata, any one of which is also applicable. Meleagrina imbricata, in 
the British Museum collection, however, representing the type most nearly coincident 
with the shell’s normally matured form, the name has been adopted in these pages. 
The growth habit of this Shark’s Bay shell is very distinct from that of the 
large tropical species. While the latter type usually occurs as solitary individuals, 
which in their matured condition lie loosely on the reef or sea-bottom, Meleagrina 
imbricata grows in dense clusters attached to one another or to other objects by 
a permanently present “byssus,” or bundle of thread-like filaments. A similar 
anchoring byssus is also possessed by Meleagrina margaritifera in its younger and 
half-grown stages, but is dispensed with on its arriving at maturity. Two characteristic 
groups of Shark’s Bay shell, in the one instance forming a social cluster and in the 
other growing on the apex of a species of Pinna, another notable byssus-secreting 
bivalve, are illustrated in Plate XXXVI. This species of Pinna or Razor shell, as 
it is locally known, with its attached clusters of Pearl shells, often occurs as crowded 
colonies, which cover acres in extent, Not unfrequently as many as forty or fifty 
Pearl-oysters are clustered together on a single Pinna shell, so that the number 
yielded by even a single acre of them is very considerable. In the larger of the two 
clusters represented in the Plate quoted, the shells are depicted at about two-thirds 
of their natural size, the two central ones only being matured specimens. This index 
to their dimensions will suffice to show how small this species is compared with its 
tropical congener, Meleagrina margaritifera. 
DD 
