Oliver. — Mollusca of the Kermadec Islands. 515 



strongly keeled midway between the periphery and the suture, the keel 

 double, enclosing the anal perforation, and becoming obsolete near the 

 outer lip. Anal perforation long and narrow, rounded behind, pointed in 

 front. Aperture pyriform, semi-detached. Outer lip at its posterior attach- 

 ment sharplv reflected and spread over the body- whorl till it joins with 

 the inner lip. Umbilicus large, deep. Sculpture : There are regular trans- 

 verse ribs on the apical whorls and part of the periphery of the body-whorl, 

 while the whole shell is crossed by fine spiral striae and faint transverse 

 growth-lines. Colour white. 



Diameter, 1 mm. 



Variations from Type. — The aperture is sometimes quite detached, and 

 the transverse ribs are more prominent in some specimens than in others, 

 while the keel may extend well up the spire. 



Habitat. — Dead shells dredged on gravelly bottom in 10 m. to 30 m. 

 near Sunday Island. 



Fissuridea bollonsi n. sp. Fig. 7. 



Description of Type Specimen. — Shell moderately elevated, height 

 041 of length, elongate-elliptical. Apex in anterior third. Anterior slope 

 straight, posterior slightly convex. Margin crenulate. Foramen elongate, 

 the sides parallel at each end, but bowed outwards in the middle third. 

 Sculpture : About 40 beaded ribs alternating with an equal number of 

 much smaller beaded riblets. Under the microscope the beads appear as 

 prominent blunt points. Colour : Above dirty white, interior white, show- 

 ing about 10 faint dark bands. 



Length, 9-2 mm. Breadth, 6 mm. Height, 3-8 mm. 



Variation from Type. — There is some variation in the proportions of the 

 shells, indicated by the following measurements. A few are depressed and 

 elongate-elliptical ; a few high, broadly elliptical, with the anterior slope 

 concave and the posterior slope much arched. These latter are old shells, 

 which, from growing normally at first, slightly alter the direction of their 

 sides. Sometimes a distinct horizontal suture is present, as though there 

 had been a resting between two growing periods. Foramen in young speci- 

 mens w r ell in front of the apex ; in adult shells it is at the apex. In many 

 individuals the colour-bands are absent. 



Length, 11-0 mm. Breadth, 7-8 mm. Height, 4-0 mm. 

 ,, 10-7 mm. ,, " 6-6 mm. ,, 3-5 mm. 



,, 10-2 mm. ,, 7-2 mm. ,, 6*0 mm. 



Habitat. — Living on rocks under a coral-like alga, South Bay, Sunday 

 Island ; plentiful. 



Tectus royanus (Iredale). 



Trochus royanus Iredale, Pro. Mai. Soc, x, 225, 1912. 

 Recorded, Iredale, I.e. 



Sculpture : In adult shells the upper surface is invariably covered with 

 algae, coralline and other, while the base usually supports a colony of 

 Serpulae. Young shells, however, show the sculpture. Suture well marked. 

 The whorls are flat, with very low rounded nodules along the lower edge, 

 there being about 15 at a distance of 2 cm. from the apex, but sometimes 

 they are so indistinct that they can scarcely be detected. The whole ex- 

 terior is ornamented by close spiral beaded ribs, about 10 to a centimetre, 

 crossed by diagonal growth-lines, and covered with a white calcareous coat- 

 ing. The base has diagonal growth-lines on a white calcareous covering, 



17* 



