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



5. DunJceria, Carpenter, 1857. 



Dunkeria falcifera, Watson (PI. XXXIV. fig. 5). 



DunJceria falcifera, Watson, Prelim. Report, pt. 7, Journ. Linn. Soc. Lond., vol. xv. p. 251. 



Station 56. May 29, 1873. Lat. 32° 8' 45" N., long. 64° 59' 35" W. Bermudas. 

 Bottom temperature 38°-2. 1000 to 1075 fathoms. Coral mud. 



Shell. — Small, high, conical, tapering a little abruptly to a fine point, longitudinally 

 and spirally ribbed, with rounded whorls and base. Sculpture: Longitudinals — in the last 

 two whorls there are 14 to 15 rather narrow and sharpish ribs ; they slowly increase in 

 number as one follows them up the spire ; on the two subembryonic whorls they suddenly 

 increase to about 30. At the top of each whorl they are small, sharp, and strongly con- 

 vex ; lower down on the whorl they are straight ; they are parted by flattish furrows 

 two to three times their breadth ; on the last whorl they are oblique and somewhat 

 irregular in form and arrangement, on the base they disappear. Besides these the 

 whole surface of ribs and furrows is scored with microscopic rounded and very distinct 

 threads. Spirals — on each whorl there are five small rounded spiral threads ; the highest 

 and strongest lies at about two-fifths of the whorl's breadth below the suture, and forms 

 an angular shoulder on the whorl, whose chief projection is at this point ; the rest are 

 pretty equally distributed on the whorl ; the fourth is weaker than the two above it, and 

 the fifth, which is still smaller, lies exactly at the suture. All of these, but especially the 

 first, rise into little sharpish knots as they cross the ribs ; on the subembryonic whorls they 

 disappear. Colour glossy, translucent white. Spire high and conical, but the upper 

 fourth of the shell tapers a little abruptly to a very fine point ; its outlines are broken by 

 the strong sutural constriction. Apex : the extreme tip is broken. Whorls : there are 8 

 below the missing embryonic one, of rapid growth in height and breadth ; they have a 

 sloping shoulder below the suture down to their point of chief breadth at the carination ; 

 from this to the third spiral, where is also a slight carination, they have a straightish 

 outline ; below this they contract on an equable curve into the suture ; the base is roundly 

 conical. Suture : its place is strongly defined by the constriction at the top and bottom 

 of each whorl and by the lowest spiral, which forms its upper edge, but it is much 

 interrupted and obscured by the curved points of the ribs, which bend round convergingly 

 into it. Mouth gibbously oval, being almost semicircular to the right and obliquely 

 straight on the body and pillar. Outer lip thin, advancing strongly at its junction 

 with the body, from which point it retreats with a rapid open curve, which produces the 

 sickle-like form of the ribs from which the species is named ; across the base it is slightly 

 flattened and patulous, with a faint open canaliculation towards the point of the pillar. 

 Pillar, with a minute but distinct twist, is very oblique in both its planes ; the 



