160 MOLLUSCA. 
of a yellowish-green colour, narrowly edged with blue; columella 
somewhat prolonged at base; edge unusually arched and provided 
with about ten sharp denticulations ; labium narrow, flat. Operculum 
pale green, inner edge strongly sinuate, rugose, inflexed; terminal 
apophysis small, erect, cylindrical; inner apophysis minute, being the 
termination of a sharp rib, revolving from the apex. 
Axis three-sixteenths of an inch; diameter one-fourth of an inch. 
This might be regarded as the young of N. polta or N. Rumphit. 
It is striated like them, but it differs in the colour of its aperture, and in 
its opercle ; and the shadowed white spots are constant and peculiar. 
Figures 192, 192 a, two views of the shell. 
NERITINA SIDEREA (Gould). 
Testa parva, ovata-globosa, polita, nitida, nigra, punctis sparsis albis 
notata: spira prominula, erosa ; anfractibus duobus vel tribus ; sutura 
marginatd: apertura semicircularis, intus caerulescens ; labio plano, 
angusto, luteo ; columella acuta, viz denticulata. Operculum fuscum. 
Neritina siderea, GouLtD; Proceed. Boston Soc. Nat. Hist., 11. 238. 
July 1847. Expedition Shells, 48. 
A small, polished, shining, jet black shell, irregularly sprinkled with 
minute white points. Its form is globular-ovate, with the spire consi- 
derably elevated, composed of two or three whorls eroded at tip, and 
with a marginal stricture just in front of the suture. The aperture is 
nearly semicircular, the inner lip rather small, plane or somewhat 
excavated, the columellar edge nearly straight, very sharp and very 
slightly denticulated, of a pale wax-yellow colour. ‘The outer lip is 
sharp, and the throat slate-coloured. The operculum is of a still darker 
slate-colour. 
Diameter one-fourth of an inch. 
Obtained at the east end of the island of Upolu, Samoa Islands. 
