THE ECONOMICS OF TfOckUS IliloticuS. 71 



The animal was illustrated by Quoy and Gaimard (Voy. Astrolabe, PI. 62, fig. 12). It is curious 

 that no epipodial filaments are shown by them. The left cervical epipodinm is shown unslit, as it 

 appears in a smoke-dried specimen before me. The radula was figured by Troschel (Das Gebiss der 

 Schnecken, ii., 1879, p. 224, pi. xxi., fig. 11, a-d). 



On what kind of sea-weed the Trochus feeds, what eggs it lays and where, as well as most details of 

 its life-history are unknown. 



Though the sexes are separate, there is no distinction between the shell of a male and of 'a 

 female animal. The reproduction of the species was- studied in New Caledonia by Mr. Montague 

 (P. D. Montague, Revue Agricole de la Xouvelle Caledonie, No. 45, 1915, pp. 39-4.3. plate I.), who 

 unfortunately was unable to continue his researches throughout the year. In shells of a diameter 

 of from 10 to 12 cm. (4J inches) he found the ripe sexual glands to extend over almost all the liver, at 

 the summit of the coil, grey in colour in the male and dark green in the female. At the end of Decem- 

 ber the ovaries of several specimens, 9 cm. in diameter, were distended with eggs ready for deposition. 

 A series of specimens ranging from 7 to 8.5 cm., examined in October and May, showed the sexual 

 glands to be small and undeveloped. 



Mr. Montague concluded, firstly, that the eggs were laid earlv in the year; secondly that the 

 animals of shells less than 8.5 cm. (3J inches) are incapable of reproduction. The latter conclusion is, 

 however, only tentative. 



Geographical Range. 



The real home of this mollusc is not, as early writers supposed, in any river, but on coral reefs. 

 It ranges from Ceylon (Hanley in Tennent, Ceylon, i., 1859, p. 241) in the west, to Samoa (Schmeltz, 

 Mus. Godeffroy, Cat. iv., 1869, p. 101) in the east, and to the Loo Choo Islands (Pilsbry, Cat. Mar. Moll. 

 Japan, 1S95, P- '79) m tne north. In Australia it was recorded by Brazier from Torres Strait and by 

 Tenison Woods from Port Douglas (Proc. Linn. Soc. N.S.YV. ii., 1878, p. 42 and v., 1880, p. 116). From 

 the Monte Bello Islands in Western Australia it has apparently been described as Trochus movtebelloensis 

 (Preston, Proc. Malac. Soc, xi., 1914, p. 16, fig. ). For food it was used by the New Caledonians 

 (Fischer, Joum. de Conch, vii., 1859, p. 331). by the islanders of Torres Strait (Jukes, Voy. Fly, i., 1847, 

 p. 17S), and by the natives of Cape Bedford, Queensland (Roth, North Q'land Ethnogr. Bull, hi., 1901, 

 p. 10). The periphery of the shell was cut out, smoothed and worn as a bracelet by the Papuans (Edge- 

 Partington, Ethnographic Album, First series, part 2, 1S90, PI. 289, fig. 5 ; PI. 290, fig. 7). But among 

 civilised people it was only known to shell fanciers until a few years ago. 



Fishing. 

 Exhaustion of former supplies of pearl shell and the increasing demand of recent years, has promoted 

 search for new sources of mother-of-pearl. Thus Trochus niloiicus, or trocas. as it is sometimes called, 

 having dense firm nacre which proved good material for buttons, came to be exploited by manufacturers. 

 During the past six years an active request for Trochus by button makers has sprung up, advancing 

 from twenty to thirty pounds a ton. The requirements of the manufacturer are that the shell shall be 

 at least an inch and a half in diameter, taken in a living state, not encrusted with algal or coralline 

 growths, nor penetrated by marine borers. According to Mr. Seale's figures, a row of buttons is cut 

 from the outside of each whorl, two rows from the base and another from the partition wall within. 

 Frequently these buttons show their origin by a trace of pink at the underside. 



Vessels formerly engaged in gathering pearl shell are now often diverted to this work. The Great 

 Barrier Reef is being fished for Trochus from Torres Strait southward to Port Mackay. The export 

 of Trochus from Queensland in 191 5 was 544 tons worth £12,000 and in 1916 was 950 tons worth 

 £23,000. The Philippine Islands export about 320 tons annually. From Western Australia the exports 

 of Trochus were : for 1912, 52 tons ; for 1913, 66. tons ; for 1914, 19 tons ; for 1915, 73 tons ; for 

 1916, 26 tons. There are large fisheries in New Guinea, the Solomon Islands and Fiji, of the product 

 of which I have no particulars. 



