192 THE NATURALIST IN AUSTRALIA. 
A somewhat grotesque name has been bestowed on one member of the 
Plectognathi by the Fremantle fishermen, with whom the Toad-fishes are familiarly 
known as “ Blow-fish.” The species in question is one of the Trunk or Cow-fishes, 
Ostracion lenticularis, differing from the type previously described, by the entire 
absence of horn-like protuberances. In recognition of its obvious natural affinity 
with the more familiar Tetrodons the title improvised for it is the “ Bony Blow-fish.” 
This list of Australian Phenomenal Fishes would be culpably incomplete without 
a brief reference to the so-called Port Jackson Shark, Cestracion Phillipi, which has 
been selected as the tail-piece illustration to this Chapter. The chief interest 
attachable to this fish is centred in its remote antiquity. It representing the only genus 
of a family group traceable back through the cretaceous and triassic to the more 
remote Devonian or carboniferous formations. For a shark, the fish is of but small 
size, rarely exceeding four or five feet in length. A tolerable idea of its form and 
peculiarities may be obtained by a reference to the figure mentioned, which was 
taken literally from life. As there shown, the head is especially large and massive, and 
provided with conspicuous brow-ridges, while in front of each of the broad dorsal fins 
there is a strong spine, as is found in the Piked Dog-fish, Acanthias, of the British seas. 
The armature of the mouth of Cestracion is highly characteristic. It consists 
in front of prehensile elements, but to the rear of these there is a pavement-like 
arrangement of crushing teeth, wherewith their owner breaks up and feeds upon 
various descriptions of hard-shelled Invertebrata. Oysters are a favourite food of this 
Shark, and, in consequence of its predilections for this bivalve, it has proved 
a formidable enemy to oyster growers in both Tasmania and on the mainland 
sea-board. At Spring Bay, in the former island Colony, the writer found it even 
necessary to fence round certain of the Government Oyster Reserves with closely 
wattled brush wood in order to protect the oyster stock laid down from this shark’s 
depredations. In some localities Cestracion feeds almost exclusively upon Sea-Urchins 
or Echini, the sharp spines of which have apparently no other effect than the pleasant 
titillation of its palate. The proof of the extent to which this piquant food is 
favoured by this Shark is afforded by the fact that the entire pavement of teeth of 
captured specimens are not unfrequently permanently stained a deep purple, through 
constant indulgence in a dietary of the commoner purple Urchin. The name of Port 
Jackson Shark was conferred upon Cestracion Phillipi with reference to its having 
been first captured in that locality, to which it was then supposed to be restricted. 
It has, however, been since found pretty well throughout temperate Australian waters, 
