UNRECORDED GENERA OF THE OLDER TERTIARY FAUNA. 174 
obtained in South Australia, as well as D. Provisi, exhibit this 
character. MMesalia belongs to Turritellide ; Diastoma, which 
has been located in at least two families, finds a resting place in 
- Cerithiide, it may be viewed as a Melania-like Cerithium. 
Until now the genus has been known only in a fossil state, in 
the Eocene and Oligocene of the Paris basin; D. Provisi occurs 
jn the Australian Miocene and Older Pliocene, and D. melanoides, 
Reeve, is living in South Australian waters. The transference 
of Mesalia melanoides, Reeve, to Diastoma will avoid the dual 
employment of the species name in J/esalia, so that IL. melanoides, 
Deshayes, may be retained. 
The genus Mesalia will however stand, as a small species, pre- 
viously overlooked, occurs in the Hocene marly clays of the 
Aldinga Cliffs. 
Drastoma PRrovist, spec. nov., Pl. x., fig. 6. 
Test very thick (in adult body-whorl 1 mm.). Shell resembling 
D. melanoides, but the coste are more slender and numerous, the 
spiral threads more neatly crenulating the coste ; the early spire- 
whorls subquadrate (not convex), whorls slightly over-lapping at 
the posterior suture (not lightly channelled), and the spiral orna- 
ment interrupted in the posterior four-fifths by a very narrow 
impressed track. In D. melanoides, the seventh spire-whorl has 
five equidistant lire; in D. Provisi, the corresponding whorl has 
five anterior equal and equidistant lire with an intervening thread- 
let, and posterior to the revolving impressed track there are about 
four slender lire; whilst there are twenty coste. The lire and 
cost increase in numbers with the revolution of the spire. 
Aperture loop-shaped, somewhat angular and slightly depressed 
in front, not detached behind ; outer lip thin; basal lip slightly 
incurved ; columella thickened and obliquely bevelled on anterior 
and inner face, callously spreading behind the columella-ridge 
(which is more sharply defined than in the recent shell). 
Dimensions :—Total length 46; width 14; length of aperture 
from posterior angle to base, 15; greatest transverse width of 
L—July 5, 1893, 
