BA8ILISSA. 423 



broken. Whorls 8 (reckoning the first two as broken), of slow and 

 regular increase till the last, which enlarges rapidly ; perfectly flat, 

 with an upper and lower border, sharply angulated and carinated at 

 the periphery, slightly convex but still very flat on the base, with a 

 blunted angulated and carinated umbilical edge. Suture linear, 

 almost invisible, niarginated above and below. Mouth perpendic- 

 ular, rhomboidal, with the body-pillar and basal edges nearly 

 equal, and the pillar and outer lip nearly parallel. Outer lip sharp 

 and thin, not patulous, not descending, advancing at its junction 

 with the body-whorl, then retreating so as to form the broad open 

 sinus, acute angled at the periphery, slightly arched across the base? 

 nicked close to the point of the pillar. Pillar-lip arched, strengthened 

 by a thin pad ; reverted on the umbilicus so as to leave a slight 

 groove behind it, it has a slight tooth in front. From the body- 

 whoi-l it bends very much over to the left, so as largely to cover the 

 umbilicus, and then it curves over to the right to join the outer lip 

 on the base at an obtuse angle. Umbilicus small, oblique edged, 

 funnel-shaped, nearly covered by the pillar-lip, contracted within, 

 scored with hair-like lines of growth. 



Alt. •255, diam. "25, least breadth '2, penultimate whorl, •075. 

 Mouth, height "12, breadth, -11 inch. ( Watson.) 



This is a narrower shell than BasUissa alia Wats., less orna- 

 mented and with a smaller umbilicus. Than Basillssa munda 

 Wats., this is a narrower shell, the flexuous longitudinals are 

 stronger, the supra-sutural bands are stronger, and in that species 

 the infra-sutural band is wanting. ( Watson.) 



Off Mouth of La Plata, 1900 fms. 



B. simplex Wats., J. L. S. L. xiv, p. 595 ; Challenger Rep., p. 

 98, t. 7, f. 6. 



B. MUNDA Watson. PI. 36, fig. 2. 



Shell broadly conical, flat on the base, sharply angulated, small, 

 thin, delicate, smooth, glossy, nacreous under a thin white calcareous 

 surface. Sculpture : there are longitudinals which are very faint 

 but still sharp, sinuated, showing the old lines of growth. Of spirals 

 there are over the whole surface very faint traces. At the bottom 

 of each whorl, about O'Ol inches above the suture, is a sharp narrow 

 thread, wdiich on the last whorl is bordered below by a second, 

 rather higher and sharper, which forms the carina, and which on the 

 spire is buried by the over-lap of the succeeding whorl. On the base 



