702 STUDIES ON AUSTRALIAN MOLLUSCA, xiii., 



species, but it was found at Clontarf Bay, N.S.W., by Mr. R. 

 Helms, and was dredged by the "Challenger" Expedition. To 

 complete the genus as developed in this State, it is now proposed 

 to insert Gibbula picturata Adams k Angas. Neither that nor 

 any other Australian species seems congeneric with magus, the 

 type of Gibbula. 



Those who consider that Moiwdonta Lamarck, 1799, is pre- 

 occupied by Monodon Linne, 1758, will employ Labio Oken, 

 1815, as the generic name. 



The animal of M. obtuna is splendidly arrayed in black and 

 gold. The edge of the muzzle is buff, followed by, first, a band 

 of black and then one of orange, the forehead-flaps are edged 

 with orange, the ocular tentacles are orange below and black 

 above, and the cervical epipodium is orange, the rest of the 

 upper surface being black. The epipodium is differentiated into 

 an anterior, median, and posterior portions. 'I'he latter begins 

 just above the tail and continues a little past the operculum; it 

 has a simple expanded margin, from beneath which spring four 

 pairs of lash-tentacles, three of which are beside the operculum, 

 and the fourth is planted where the cervical meets the posterior 

 epipodium. At the base of each lash is set a stump-tentacle, 

 forming an uneven pair like the ocular and cephalic tentacles; 

 the three hinder tentacles are each adnate to their associate 

 stumps, but the anterior lash is parted from its stump, while a 

 stump without a lash stands in the median line behind the oper- 

 culum. Another lonely stump is the cervical papilla, which 

 occurs on both left and right sides. The medium epipodium or 

 cervical lobe extends from the ocular tentacle to the anterior 

 lash. On the right, it has a plain edge and during locomotion 

 is curled into a makesliift siphon and extruded beyond the lip of 

 the shell. On the left, the edge is cut up into about twenty 

 filaments. The ocular tentacles are compressed from above to 

 below and keeled laterally, thus indicating that they are over- 

 run by the epipodium, which finds its anterior expression in a 

 pair of forehead-flaps on the snout. Even when the animal has 

 withdrawn into the shell, the epipodial lashes steal out from 

 behind the operculum and softly search. 



