185 



NOTES ON A EECENT DBEDG-ING TEIP IN THE 



DEEWENT. 



By A. Morton, E.L.S. 



The Tasmanian Fisheries Commissioners having decided to 

 examine the several bays in the river Derwent, for the 

 purpose of ascertaining whether, as in former times, there 

 still existed natural oyster beds, advantage was taken of the 

 opportunity to pay special attention to the marine fauna that 

 might bo obtained by the means of the dredge. Mr. A. 

 Durrand, F.E.M.A., a gentlemen on a visit to Tasmania, who 

 has made a collection of Foraminifera from many parts of the 

 southern seas, accompanied us on our trip. 



Several bays to the northward of the harbour were tried, 

 put the dredge failed to secure any specimens of oysters, and 

 m only one or two instances did we obtain any dead shells. 

 Although from a commercial point of view the result of the 

 dredging trip proved comparatively a failure, still from a 

 scientific point we were amply rewarded. Instead of 

 finding the Oyster, a large quantity of Pectens or Scallops 

 were obtained. Pecten meridonalis, P. bifrons, and P. 

 asperrimus. As has already been pointed out by Mr. Seager, 

 the Secretary to the Fisheries Commission, a large number of 

 this shell fish can be obtained in the river Derwent by means 

 °i the dredge, the quality being equal to the European 

 Scallops, it is to be hoped that steps will be taken by our 

 fishermen to place in the market this class of shell fish that 

 should readily find consumers. As the places we dredged in 

 were rather far up the river, the number of species of 

 Mollusca were naturally limited, those obtained belonging to 

 the genus Cardium, Fusus, Triton, Elenchus, and a few others 

 Well known. A largo number of a pretty shell known as 

 Modiolaria Oumingiana, Dunker, were met with, inhabiting 

 tue sponge, and embedded in the larger kind of Ascidians. 

 lhis shell is common in the Australian waters and also in New 

 Caledonia. Several Crustaceans, chiefly of the smaller kind, 

 Were obtained, one kind being found in great numbers 

 inhabiting the common Mussel. This peculiar little Crab, 

 belonging to the genus Pinnotheridce Pinnotheres pisium, 

 Jjeach, I find has a very wide range common in the European 

 seas, and although found inhabiting the Mussel of New 

 fjealand, has not yet, I am informed by Mr. Thos. Whitelegge, 

 the able Zoologist of the Australian Museum, Sydney, been 

 observed in the Mussel found round the New South Wales coast. 



Professor Hutton, Professor of Biology of the Christchurch 



nivers ity, New Zealand, on receiving two or three examples 

 of tiiis Crab writes as follows :— 



-The male Pinnotheres pisium does not live in the bivalve, 



but wanders about; consequently he is rare, and only got by 



chance. I do not think the Crabs hurt the Mussels." I am, 



uowevei^ of opinion that occasionally the male Crab is found 



r equenting the bivalve, as among some 30 or 40 specimens 



