712 STUDIES ON AUSTRALIAN MOLLUSCA, xiii., 



The radula (Fig. 30) has a rachidian with arched base, three 

 median pointed cusps and a small external one; laterals bicuspid, 

 the inner cusp half the size of its fellow, with two small denticles 

 on its inner blade, the outer cusp slender and falcate. 



Arcularia particeps Hedley. 

 (Plate xlix., fig.20.) 

 This species was named, antea, Vol. xxxix., p.738. The animal 

 lives sunk beneath the surface of the sand. Into a pool where 

 no Arcularia were visible, a few crushed shellfish were thrown; 

 a few minutes afterwards a number of individuals, including the 

 subject of my sketch, appeared in various directions, all steadily 

 crawling towards the bait. The animal of A. particeps is par- 

 ticularly bold and active. When lifted out of the water by the 

 shell, the animal twists and kicks about with much vigour. The 

 colour of it is cream irregularly splashed with black. 



Xymene hanleyi Angas. 

 (Plate xlix., figs.21, 22, 23, 24.) 



Trophon hanleyi Angas, Proc. Zool. Soc, 1867, p. 110, PL xiii., 

 fig.l. 



In previous papers, I have figured the young shell of this, 

 under the title of Trophon paivce (a7itea,Y(A. xxxiii., p. 456), and 

 later noted that Tryon made a mistake in subordinating T. 

 hanleyi to T. paivce (antea, Vol. xxxviii., p. 329). For this 

 group, Hutton introduced the genus Kalydon, but Iredale, on the 

 ground that Kalydon was preoccupied, has substituted Xymene* 



The animal (Fig. 21) is very common under stones in the mud- 

 zone in Sydney Harbour, where it is notorious as an oyster-pest, t 

 The eggs (Figs. 2 3, 24) are laid in separate packets, each packet 

 round, about 5 mm. in diameter, rather flatter than hemispherical, 

 with a central circular oiifice about l'5mm. across. The ova 

 are visible both through the orifice and through the semitrans- 

 parent membrane. These eggs are deposited on the under 

 surface of shells and stones. So crowded are they, that Mr. T. 



* Iredale, Trans. N.Z. Inst., xlvii, 1915, p.471. 

 t Saville Kent, Parliamentary Report on Oysters and Oyster-Fisheries 

 of Queensland, 1891, p. lU, PI. i., tigs.l, lU, 11, 



