146. 
South Australian Shells. 
S.A. NAT., VOL. XIV. 
August 31st. 1933. 
with minute growth rings at irregular intervals, solid at apex, thin 
at aperture; milk-white opaque rings alternate with pale-orange 
translucent ones; supplementary tube a small round pipe excen- 
tric to the direction of the shell and arising in the centre of the 
apex. Length 10.5, diam, at aperture 1.1, at apex. .62 mm; 
diam. of tube .2 mm. Dredged — Cape Borda, Cape Jaffa, Nep- 
tune Islands, Beachport, 60-200 fathoms. (Type locality — 
Numerous examples were taken in 63-75 fathoms off Port Kembla 
N.S.W.). Some South Australian examples have slight annular 
constrictions at intervals of 3 mm: here the shell is less opaque- 
white, and the opacity gradually increases ' anteriorly. 'Lhc ap- 
pendix is visible in very early life, when the shell is extremely 
narrow. \Mien the appendix is absent in the earl)- stages of 
growth the shell is not unlike juvenile D. lubricatvm Sowerby, 
but does not increase so rapidly, and has more marked trans- 
verse striations. 
D. hyperhemileuron Verco 1011. PI. I, figs. 3 and 3a. 
Long, narrow, very slightly curved, mostly at hinder part, rather 
thin; white when dead, translucent when fresh, and glistening; 
axial ribs, twelve, invalid, narrow, ^no increase in number with 
age, becoming obsolete early, so as to leave the anterior two- 
thirds of shell smooth but for very fine accremental scratch lines; 
interstices nearly flat, slightly concave; anterior orifice round, 
margin thin and simple; posterior end truncated, with a long 
narrow diaphanous appendix directed eccentrically dorsally; the 
growth lines on the appendix form a convexly bordered sinus on 
the ventral surface about as wide as deep, and a scarcely de- 
pressed margin on the dorsal surface. Length 20.5, greatest 
width 1.8, least .7 mm., length of appendix 2.2, diam. A mm. 
Western Australia — King George Sound, 12-14 fathoms, 200 ex- 
amples, several alive, (Type locality), also Geographe Bay, Fre- 
mantle, 10-15 fathoms. Some individuals with perfect posterior 
ends run down to a diameter of .3 mm., and are there diaphanous 
and ribless, and have only growth striae; others more mature 
and with a posterior end of I mm. in diameter, and without an 
appendix, are here bevelled internally and thinner on the conv'ex 
side, where there is a shallow triangular notch. The largest 
example is 30.75 x 2.3 mm. The ribs may vary in number 
from ten to sixteen in different individuals. The species closely 
resembles /). hcmileuron V'erco, in the ribless anterior portion 
and the never increasing ribs of the posterior end, and in their 
extension to within 2 mm. of the end in very young individuals 
and in the ventral notch at the hinder extremity; but the latter 
