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hitherto known. Its auricles are narrow, convex above, and hollow 
beneath, or in form of a short canal. 
Operculum oval, flat above, flesh-coloured, and radiated from the 
summit to the anterior side with five to seven blackish lines; the 
anterior side bordered with a blood-coloured zone, enclosed by an- 
other pellucid zone; very fine striz spring from the summit, and 
radiate to the anterior side in an opposite direction to the bands. 
Inferior surface less flat, pale rosy brown or reddish brown, as well 
as the teeth, which offer nothing particular, and which resemble 
those of the opercula of Ner. pulligera and other allied species. The 
operculum of var. 6 is of an uniform colour above, on account of 
its zones being confluent. Thut of var. y is of a very pale green, 
with a circular stria, which divides its external surface in two parts 
almost longitudinally. This character is also observable upon the 
operculum of var. (3, but very faintly. There is no trace-of it upon 
the type. 
*** Spinose, interdum muticze (Clithon, Montfort). 
11. Nerrra ortvacea. UN. testd ovato-globosd, ventricosd, crassd, 
griseo-olivaced, anfractibus 25, superne depressiusculis ; apice sub- 
convexo, obtuso, laterali, in medio deroso ; aperturd extis subqua- 
dratd, intis exalbidd, labio postice rufescente, plano, margine 
crenato, et in medio vir arcuato. 
Long. 1°12; lat. 1°36; conv. 0°76 poll. 
Hab. Agoo, province of Pangasinan, island of Lugon: on stones 
in a rapid river. 
This Clithon has sometimes a brownish zone posteriorly, with some 
faint reddish spots. The summit of the shell is corroded and exca- 
vated. Operculum of a Clithon, rosy white, spotted with red at the 
summit, and faintly marked with a circular streak in the centre of 
its external surface. The interior surface is reddish, convex, and 
flattened at the base ; two teeth at the top, the upper one lamellated, 
elevated into an obtuse point; the second or inferior one circular 
and striated. Underneath this tooth there is a great depression. 
12. Nerira sicotor. UN. testd ventricoso-ovatd, crassiusculd, sub 
suturd depressiusculd, strigis nigris et olivaceis longitudinalibus 
dense pictd; apice eroso; aperturd extis subquadratd exalbidd; labio 
plano, superne calloso basi canaliculato, margine in medio arcuato, 
et obsolete dentato ; dente cardinali majori. 
Long. 1:04; lat. 1-20; conv. 0°76 poll. 
Hab. Agoo: in a mountain-stream. 
Operculum of a Clithon, oval, solid, whitish, striated lengthwise 
in an oblique direction, and marked with a circular furrow from the 
summit to the posterior margin, ending in a slight notch; inferior 
surface furnished with a large, circular, slightly raised rib, prolonged 
in an obtuse angle at the posterior margin. Two teeth at the top: 
the upper one an oblique rosy plate terminated at the summit; the 
lower one circular, delicate yellow, enlarged at the summit, and 
striated lengthwise and across. 
