-MOORE——AUSTRALIAN MESOZOIC GHOLOGY.- 257 
63. Natrca oRNATISSIMA, sp.n. Pl. X. fig. 16, 
Shell small; spire depressed ; whorls convex, the last very rounded 
and globose; aperture large and circular. 
Shell-structure smooth, with broad bands of growth at intervals, 
within or on the surface of which are finer striations. The shell 
still retains some of its original colour. 
One specimen only, from Wollumbilla. 
64, RissoINa AUSTRALIS, sp.n. Pl. X. fig. 23. 
Shell very small, moderately elevated,, spire consisting of five 
rounded or convex volutions, with distinct rounded sutures, which 
are ornamented with numerous longitudinal coste. 
This shell, which is very minute, is from Western Australia, Only 
one specimen has been recognized. 
65, Turpo AusTRauis, sp.n. Pl. X. figs. 17 & 18. 
Shell small, discoidal; spire obtuse and much depressed ; whorls 4, 
the outer circumference convex; surface with slightly curved, de- 
pressed lines of growth; mouth large, ovate. 
This shell is from Western Australia, 
66. CRIocERAS AUSTRALE, sp.n. PI. XY. fig. 3. 
Shell very large, discoidal; whorls rounded, incurved, the inner 
whorls rather closely fitting but separate. In the younger state, as 
seen in the reduced figure, the shell possesses regular rounded 
slightly curved ribs with intervening rounded sulci, which increase 
in width with the age of the shell. In the adult shell the ribs 
become widely separated, the largest chamber measuring at the back 
34 inches, and they possess very acute ridges, with two depressed 
bosses on either side, the depressions between the ribs being regu- 
larly concave. 
The block containing the last five chambers of the shell is slightly 
compressed on the back; and, though it is not complete, the mouth 
measures 74 inches in depth by 7 inches in breadth. The siphuncu- 
cular tube is small and situated immediately under the back of the 
shell. 
There appears no reason to doubt that the larger chambers belong 
to the smaller whorls, though the connecting portions are wanting. 
When complete, it is probable the shell attained nearly twice the 
dimensions of the C. Bowerbankii of the Lower Greensand. Its 
ornamentation is proportionally much coarser than in that species. — 
On the interior of the shell are attached Polyzoa, Serpule, and 
other remains identical with those on the interior of the Cytherea 
Clarket previously noticed, from which there appears no doubt that 
that shell and the Crioceras are identical in age; and as no example 
of Crioceras has yet been obtained out of the Neocomian period, 
it is reasonable to infer that they represent it on the Australian 
continent. 
It is irom the district of the Upper Maranoa. 
