BASILISSA. 



427 



flexuously ribbed. Sculpture : the whole surface is covered with 

 longitudinal flexuous ribs, which are narrow, sharp, and uniform ; 

 each of these is about 0*002 in. broad, and they are parted by intervals 

 which at the suture are twice and at the periphery thrice as broad 

 as the ribs. There are about forty of these on the last whorl. They 

 are crossed by spirals, half the breadth of the ribs, running across the 

 intercostal spaces and forming knobs on the ribs. Of these spirals 

 there are about seventeen on the last whorl, much closer set and 

 less uniform than the ribs ; in particular the carinal spiral, which is 

 very sharp, and the fourth and seventh above it, are stronger than 

 the others ; the last mentioned of these is especially so on the earliest 

 whorls. On the base the longitudinals though continued even into 

 the umbilicus, become much less prominent and are no longer 

 nodose ; and the spirals, of which there are about fifteen, are closer 

 set, broader and flatter, except the first three below the carina, which 

 are sharp and narrow. The whole base is pit-marked from the spiral 

 interstitial furrows being cut up by the longitudinals. Color dead 

 white (on the base a little glossy) on the thin porcelaneous surface, 

 through which ihe nacreous layer behind gleams. Spire raised, with 

 a very slightly concave outline. Apex, which consists of the minute 

 smooth embryonic whorl and a half, is itself a little flattened, but 

 rises sharply above the sculptured surface of the succeeding whorls. 

 Whorls 5?, of slow and regular increase till the last, which begins 

 to enlarge rapidly ; they are slightly rounded above, very sharply 

 angulated at the keel, and flattened on the base, with a bluntly 

 angulated umbilical edge. Suture distinct, slightly impressed. 

 Mouth perpendicular, square. Outer lip sharp, thickened by a slight 

 internal remote callus, not patulous, not descending, advancing at its 

 junction with the body-whorl and then slightly retreating so as to 

 form the very shallow open sinus ; right-angled at the periphery, 

 flat on the base, w'here it retreats so as to form two rounded sinuses, 

 making with the pillar an angle that is scarcely obtuse. Pillar-lip 

 is straight, a little thickened and reverted, so as to leave a slight 

 groove behind it. It advances on the body-whorl, then retreats so 

 as to form a feeble sinus, bending at the same time shortly but 

 sharply to the right into the umbilicus and then advancing straight 

 forward, but a little toward the left, to its junction with the outer 

 lip at the base. Umbilicus funnel-shaped, open-mouthed, oblique- 

 edged, straight-sided, deep and contracted internally. Its edge is 

 sharply defined by a spiral thread, and is obliquely scored by the 



