498 MOLLUSCA OF MAST HEAD REEF, QUEENSLAND, II., 



A couple of specimens from 17-20 fathoms. A single speci- 

 men, more delicately sculptured than the type, occurred in 5-10 

 fathoms off the Hope Islands, North Queensland. 



Named after a member of the Expedition, Mr. H. L. Kesteven. 



ClTHNA MARMORATA, n.Sp. 



(Plate xviii., figs.27-28,) 



Shell smrJl, thin, hyaline, imperforate, conical. Whorls six, 

 parted by impressed sutures, rounded, but inclining to be angled 

 at the periphery in some individuals. Sculpture: fine growth- 

 lines. Colour: on a hyaline background are numerous narrow 

 zigzag brown radial lines. These are interrupted by a peripheral 

 band, chequered b}^ small square opaque white dots, which ascends 

 the spire above the suture. Aperture subquadrate, emarginate 

 and subchannelled anteriorly, outer lip flexuous, sometimes with 

 an external varix; columella with a low oblique median fold and 

 a narrow callus reflection adnate to the axis. Height 1-95 mm.; 

 breadth I'l mm. 



Common in 17-20 fathoms. I have also dredged it in 5-10 

 fathoms off the Hope Islands near Cooktown. 



Plesiotrochus pagodiformis, n.sp. 



(Plate xvii., fig. 16.) 



Shell small, solid, regularly conical. Whorls eight, including 

 the protoconch. Colour buff or white, with or without irregular 

 chocolate streaks or dots. Sculpture: a broad, deep, peripheral 

 groove indents the body-whorl and ascends the spire; the top side 

 of the groove overhangs the lower, giving a pagodiform shape to 

 the shell; the suture is wound outside the basal slope of the 

 groove; on the earlier whorls the upper limb of this groove is 

 pinched into a sharper keel. Broad but low radial ribs, which 

 vary in development in different individuals, cross the whorls. 

 They are faint in the earlier whorls and grow bolder with the 

 increase of the shell, do not continue from whorl to whorl, and 

 amount to about seven on the last volution, are scarcely per- 



