S.A. NAT.. VOL. XIV. 
Aucust 31st, 1933. By Bernard C. Cotton and F. K. Godfrey. 1_43 . 
no slit or notch. Length 19, diam. aperture 2.8, apex 1.3 inm. 
Gulf St. Vincent, 15-22 fathoms. (Type locality — Gulf St. Vin- 
cent, South Australia). Many specimens dredged with seven 
ribs posteriorly and a varying number anteriorly. Probably the 
D. octogonum of Adcock's list, a synonym of Z). octangulatum 
Donovan. 
D. octopleuron Verco 1911 (not D. octagomim Lamarck 
[Angas, Proc. Zool. Soc., 1878. p.8681). “The Eight-ribbed Den- 
talium.” This shell is like D. bednalli Pilsbry & Sharp, except 
that it has eight ribs at the posterior end instead of seven. In 
four specimens the eight costae run throughout the shell, which 
may measure 20 mm. in length. But in all the others rihlets 
arise; it may be in only one or in two, or up to all the inter- 
costal spaces. These riblets may number as many as four in a 
space; they may equal in size the primary ribs, if they are few, 
or they may remain small, especially if numerous. (Type local- 
ity' — Gulf St. Vincent, 15-22 fathoms). \'erco dredged 88 in 
good condition in this locality. This variety is the most common 
In our shallower waters, and this would be the form found by 
Angas on Henley Beach and named by h.im D. ociagomiiv, 
D, robustum Brazier 1877. “The Ri>bust Dentalium.’' 
Nearly straight, thick, dull white; axial ribs nine, rounded, wide 
apart, narrow toward the apex, interstices flattened, smooth; apex 
with small perforation, entire; aperture thickened, regular. Length 
20, diam. apex .75, base 2.5 mm. Gulf St. \ incent. 15-22 fathoms. 
(Type locality — Katow, New Guinea, 8 fathoms, sandy mud and 
coral). Some specimens dredged in Gulf St. Vincent have nine 
ribs posteriorly and more than nine anteriorly, 
D. decemcostatum Brazier 1 877. “The Ten-ribbed Dcn- 
talium.” Tapering, thin, slightly arched, white; axial ribs ten, 
somewhat sharp, interstices nearly flat; transverse striations fine; 
apex with a small perforation; basal aperture large, circular. 
Length 20, diam. apex .5, base 3 mm. Gulf St. Vincent 15-22 
fathoms. (Type locality — Katow, New Guinea, 8 fathoms, sandy 
mud). Some specimens dredged in Gulf St. \ incent have ten 
ribs posteriorly, and more than ten anteriorly. 
D. francisense Verco 1911. PI. 1, figs. 1 and la. “Ihe 
St. Francis Island Dentalium.'' Moderateh’ solid, narrow.^ curv- 
ed, less anteriorly, translucent white; ribs fourteen, broad, low, 
round, extending throughout, separated by distinct linear inter- 
spaces; growth lines microscQpic; ant'ecior aperture circular, 
margins thin, scarcely scalloped: posterior end truncated, a'per- 
ture small, border thick, shape oval, elongate antero-postenorly . 
Length 28, diam. ant. 3.2, post. 1.6 mm. St. hrancis Island; Gulf 
St. Vincent; Cape Borda; 15-55 fathoms. Also Western Aus- 
