144 . 
S.A. NAT.^ VOL. XIV. 
August 31st. 193.T. 
South Australian Shells. 
tralia — beach — Bunbury, Rottnest Island; di^edged — Hopetoun, 
Ccographe Bay, Fremantle, 6-35 fathoms. (Type locality — 15- 
20 fathoms. Petrel Bay. St. Francis Island, South Australia). 
Tills shell varies. A much younger individual than the t\'pe 
measures 13,5 x 2.4 x .8 min, is much more curved and has a 
slightly projecting appendical tube. I'here may be only eleven 
ribs throughout: or eleven posteriori)', and more anteriorly up 
to t\veiU)'-t\vo from intercalcated rlblets; there ma\' be twelve 
I'ibs throughout and these may be typically broad and round, or 
rather narrow and flat; there may be thirteen, fifteen, or vcr\ 
rarel)' eighteen ribs throughout. \'erco writes, '‘I am inclined 
to think that even this species is but an exteme variant of 7X 
intcrcalat urn Gould. It would seem as though the more initial 
ribs are present at tlie posterior end, the fewer interstitial ribs 
arise, which is easih' understood; and the more likely they are to 
be rtnmd and broad and encroach on the intercostal spaces. Still 
one may meet with an occasional specimen starting with eleven 
ribs wliich increase up to twenty-four, and are rather narrow; or 
with one which starts with onl)' a few ribs, seven or nine, and 
these become broad and rounded. 
D. hemileuron \^erco 1911. PI. 1, fie. 2. Loncx nanow, 
rather thick, ver\' slightly curved, mostly at the hinder part: 
white opaque when dead, translucent when fresh, and glistening; 
axial ribs ten. valid, narrow, about one fourth the width of their 
interspaces, less \'alid and less distant on the convex side, ’well 
deveh)j'.cd in the posterior half, then becoming quickly obsolete 
and absent Irom the anterior third; ribs do not increase in num- 
ber ^^■ith age; transverse scratch marks, close, and circles of var)'- 
ing o]''acit\'; anterior aperture round; posterior aperture rounds but 
on the convex surface It lias a sinus about as deep as wide with 
convex margins. Length 30, greatest width 2.4, smallest .4 mm. 
Cape Jaffa; Beachport; 130-300 fathoms. (Type locality — 300 
fathoms off Cape Jafi'a, South Australia). Some examples have 
nine ribs, some eight, Sfune eleven. There are no axial intersti- 
tial riblets as in D. ihetidis Hedlety nor increase in the number 
of ribs b)’ splitting or Intercalation, as In D. inlrrcalatinn Gould, 
and the anterior part is libless. 
D. tasmaniensis d'enison-Woods 1876. “The Tasmanian 
Dentalium." Solid, slender, slowly increasing, slightl)' curved, 
white; axial ribs eight. Interstices often subcostate; apex entire. 
Length 10.5, diam. apex .5 mm. Port Adelaide River, (d’ype 
localit)' — Xorthwest coast of Tasmania). A gracefully tapering 
shell, curved slightly, with valid ribs and often smaller ones in 
the interstices. D. aratinn Tate and D. nanum Hutton, of the 
South Australian and New Zealand tertiaries relati\'el)', arc allied 
