444 THE VOYAGE OF H.M.S. CHALLENGEK. 



16. Natica pseustes, 1 Watson (PI. XXVII. fig. 3). 



Natica pseustes, Watson, Prelim. Keport, pt. 7, Journ. Linn. Soc. Lond., vol. xv. p. 255. 



July 1874. Levuka, Fiji. Shallow water. 



Shell, — Rounded, with no angulation in the whole contour, obliquely depressedly 

 globose, with spire scarcely projecting, thin, smooth, glossy, porcellanous white, with a 

 zone of large chestnut irregular spots below the suture ; the umbilicus and pillar are 

 uniformly stained with the same colour. Sculpture : Longitudinals — there are many 

 delicate hair-like lines of growth, which are strongest and most crowded near the suture 

 and round the umbilicus. Spirals — there is a very faint appearance of rounded threads 

 and furrows, one of which below the suture is a little stronger than the rest ; besides these 

 the surface is densely, delicately, sharply, microscopically scratched ; these scratches are 

 strongest on the upper part of the last whorl near the mouth, where their intersection 

 with the lines of growth produces a very delicate sharp cross-hatching. The centre of the 

 base has a scarce perceptible carination, which becomes stronger just behind the point of 

 the pillar ; within this carination is a strong but shallow umbilical furrow, which deeply 

 cuts in on the pillar, and curves round the base of the strong pad which chokes up the 

 umbilicus. Colour semi-transparent, porcellanous white, which becomes a dead white 

 round the umbilicus and also in a broadish band below the suture ; this white band is 

 flecked with irregular, sharply defined, ruddy chestnut spots ; a stain of this colour in a 

 lighter shade suffuses the whole umbilicus and pillar : the rest of the shell is covered with 

 a delicate network of fine, sharply defined light-chestnut lines ; amidst this network are 

 two or three spiral zones, where the brown lines are sparser and pale lanceolate spots 

 appear. Epidermis: none visible. Spire scarcely raised, but just perceptibly conical. 

 Apex rather large, with the extreme rounded tip appearing at the highest point of the 

 shell. Wliorls 4f (of which the first 2^ are embryonic and glassy), very flatly rounded, 

 of rather slow increase. Suture almost horizontal and very slight. Mouth very oblique, 

 semicircular, but pointed above and rounded below, with a slight angulation at the front 

 of the pillar ; the filling up of the superior corner by the labial pad equalizes the two 

 extremities and reduces the opening to an unequal-sided oval ; its entire height is 

 about It of the whole height of the shell ; it is open, transparent porcellanous white 

 within. Outer lip : it advances slightly on leaving the body-whorl, but beyond the pad 

 retreats a very little, and from this point its whole curve is very equable ; its edge is blunt 

 and rounded. Inner lip very slightly concave ; at the upper angle of the mouth it is 

 formed by a thick transparently porcellanous pad, which is faintly tinged with chestnut : 

 this pad projects beyond the plane of the mouth in a point, which is separated from the 

 outer lip by a little triangular depression ; it is continued with an uneven surface across 

 the body, and unites with the pad which closes the upper part of the umbilicus, and is 

 connected with the great chestnut- coloured spiral buttress which chokes up the umbilicus, 



1 4/fuirs-?].-, a deceiver. 



