102 THE VOYAGE OF H.M.S. CHALLENGER. 



the base of the whorls. This whitish fillet extends to the base, where it forms a narrow 

 obliquely-corrugated edging. On the base there are about thirty spirals, more crowded, 

 flattened, and irregular than above, and the edge of the umbilicus is defined by another 

 whitish fillet, ornamented with about thirty oblong beads. One or two smaller and more 

 faintly beaded threads lie within the edge of the umbilicus. Longitudinals — there are of 

 these on the last whorl about 120, flexuous, marking the lines of growth, rather stronger, 

 more regular, and more distant than the spirals, which run over the top of them and form 

 little white nodes at the crossings. The intersections of these two systems cut the whole 

 surface into rhombic reticulations, whose breadth is about O'Oll and their height 0006. 

 The longitudinal threads themselves are about 0'005 and the spirals about 0'003 broad. 

 On the base the longitudinals are flattened and spread out into undulations. Colour 

 creamy, on a dull polished surface, with a very faint nacreous gleam, which is pearly 

 within the mouth ; the apex is ruddy. Spire high and conical, with slightly concave 

 slopes ; apex broken. On the upper whorls the longitudinals are strong, while the spirals 

 are obsolete, except the carinal fillet, which projects bluntly above the suture. Wlwrls 

 about 14, of very regular increase, very slightly convex, sharply acute-angled at the 

 carina ; on the base, flat at the outer edge and barely convex in the middle, with a slight 

 dip in toward the edge of the umbilicus, which is strongly defined. Suture linear, defined 

 by the white carinal fillet, and also on the lower whorls by being very slightly impressed. 

 Mouth perpendicular, rhomboidal, the basal and palatal lines being parallel, the other 

 two are somewhat diverging and curved, broader than high. Outer lip sharp and thin, 

 not patulous, not descending, with a shallow open sinus below the suture, then, about 

 the middle of the whorl, it advances with a rounded sweep, retreating sharply across the 

 carina to form the open rounded basal sinus towards the outer edge of the base. Pillar-lip 

 sharp and thin ; it rises from the body a good way within the edge of the umbilicus. It 

 retreats so as to form a sinus, and there it bends over a little on the umbilicus, and it 

 forms a sharp angle projecting into a tooth at the extreme point of the pillar. Umbilicus 

 strong, deep, abrupt, there being on the base only a very slight dip in towards it, and it 

 is defined by the white-beaded fillet. Within, besides the two spiral lines, there are slight 

 longitudinal striations, and the inner edge of the whorls twines like a staircase round it, 

 but concealed by the over-curve of the pillar-lip. H. 075 in. B. 0G5, least 0'6. Penulti- 

 mate whorl, 0-16. Mouth, height 0"2, breadth 0"28. 



The form of this shell connects it with Basilissa alta, Basilissa simplex, and JBasilissa mundctj and 

 it distinctly has the sinuses of the genus : the layer of nacre is very faint ; there is, however, a gleam 

 of it through the surface-layer, and within the mouth, in a favourable light and protected from light 

 coming through the shell, there is a distinct pearly lustre. 



It has some resemblance to Eutroclms gemmatus, Reeve, in form and in its gemmed umbilicus ; 

 and, though much higher and more conical, recalls the Solaria of the group Torinia (Gray), especially 

 Solarium Irochoides, Desh. 



