262 
ences, D. Manielli enlarges more rapidly, and the costation is 
acute, elevated, and regularly disposed, primary and secondary 
cost alternating; in D. Kickxi the costations are broad, 
depressed, and irregularly disposed, anteriorly they are more 
numerous than in the Australian species. 
D. latesuclatum, spec. nov. PI. viii., fig. 9. 
Shell nearly straight, nine-angled (rarely twelve-angled) of 
rapid increase, being about seven times as long as wide. Surface 
ornamented with nine (rarely twelve), strong, elevated ridges, 
which are somewhat compressed at the sides and roundly 
truncated atop; the ridges are somewhat irregularly disposed 
being closer together on the convex aspect and fewer on the con- 
cave aspect, they extend from the apex in undiminished strength 
to the oral aperture ; the concave furrows at the apex are of 
about equal width with the ridges, thence they increase in breadth 
till at the oral aperture they are on the convex aspect from two — 
to three times as wide as the ridges, and as much as four times 
on the concave aspect. The interstitial furrows in the basal 
portion may have a few longitudinal threads and striz, and are 
traversed by sub-distant incremental lines which pass over the 
coste. 
a truncated with a long narrow slit on the convex face, no 
plug ; the aperture is circular internally, polygonal externally ; 
oral aperture with a thin acute margin (thus indicating a perfect 
shell) of a polygonal outline. 
Length, 40; breadth of oral aperture, 6—7 mill. 
MIOCENE. —In the basal clay-bed at GRANGE Burn near Hamil- 
ton, Victoria ‘nine examples). 
Among species of the same section having a prominent poly- 
gonal transverse section the Grangeburn fossil makes a closer 
agreement with D. striatum, Lamarck, as figured by Deshayes, 
Mon. Dentale, than with any other, but it is abbreviated in 
length and is broader, has nine ridges, not twelve to fourteen. 
There are, however, some species in Section Dentalium (restricted) 
which Offer some Site! such as elephantinum, aprinum, &c. 
It is not likely to be mistaken for D. Mantelli with its numerous 
and slender ribs, which are evanscent at the anterior one-third or 
thereabouts. 
Section GraptracmE, Pilsbry and Sharp, 1897. 
Surface sculptured with close, fine, deeply engraved, longi- 
tudinal strie near the apex. 
D. sectiforme, spec. nov. Pl. viii., figs. 6-6a 
Shell small, very slender, very little tapering, slightly arched, 
translucent-white and shining. Sculpture of very numerous, 
