GAZA. 155 



luicini are a few denticles. There are five lateral teeth, and 

 between twenty and thirty uncini. (DalL) 



The nucleus of G. superba is often caducous, and in such speci- 

 mens the apex is pierced with a circular perforation 1'. mill, in 

 diain., which is continuous with the umbilicus. There does not 

 appear to be any particular diflTerence between the nucleus and the 

 ■early whorls, its loss would therefore seem to be due merely to its 

 fragility. In none of those in which it remains is there any indica- 

 tion of its being reinforced by a shelly deposit. (DalL) 



I regard Gaza and its subgenera as a grou]:) of Trochidce re- 

 lated to Lunella of the Turbinidce on the one hand, and Umboniwn 

 on the other. (DalL) 



Our knowledge of this beautiful group is derived wholly from 

 the publications of Watson and of Dai.l. The species are all deep 

 sea dwellers, living mostly at depths of 100 fms. or greater. 



O. d^dala Watson. PI. 36, fig. 12. 



Shell depressedly globose, with a convexly conical spire, thin, 

 translucent, horny, nacreous in its whole texture, and iridescent on 

 the surface, with a slightly reverted and narrowly thickened lip, a 

 thin edged twisted pillar, the point of which runs out into a 

 bluntly mucronated angle. Sculpture : Longitudinals — the whole 

 surface is covered with strong, puckered, oblique lines of growth, 

 which are sharp-edged but flattened, rather regular, with many 

 minuter ones in the intervals. The longitudinals are cross- 

 hatched with spirals, which are stronger and more regular, but not 

 perfectly uniform, consisting of square threads and furrows of equal 

 breadth, and both scored by the longitudinals ; on the earlier whorls 

 these spirals disappear before the longitudinals do ; and on the base 

 they become on the outside feebler, closer, and finer, in the middle 

 broader and flatter, and stronger again toward the centre of the 

 shell. Color, delicate yellowish, with a horny translucency and ex- 

 quisite iridescence, Avhich under the lens appears brilliant. Spire 

 high and slightly scalar. Apex very small, flatly rounded, the 

 embryonic li whorl very slightly projecting. Whorls 7 of gradual 

 increase, well rounded, the last slightly angulated below, and on 

 the base flattened, but rather less so towards the mouth, where there 

 is a slight contraction and downward turning of the whole whorl, 

 without, however, any descending of the lip at its junction with the 

 body. Suture very distinct, but not impressed, mouth rather large, 

 very oblique, semioval. Outer lip reflected and thickened internally 



