152 MESOZOIC FOSSILS FROM THE PALMER RIVER, QUEENSLAND, 
quite blunt. M. Astier*, a great authority on the genus, is ag 
opinion that all species of Crioceras become Ancyloceras in their 
adult state, and that in the former genus we never find the perfect 
mouth of the adult shell. Again, Pictet} states with regard to 
Toxoceras that, from certain facts he had observed amongst the 
fossils of Switzerland and Savoy, he believed that the Tomoceras 
form and Ancyloceras form entirely depended on mode of growth. 
This was even in the same species so variable that one specimen 
might be referred to a Toweceras and another was so unrolled as 
tobean Ancyloceras. In the present species the first whorlas far as 
the termination of the tubercular ribs is clearly of the Zowoceras 
form, and if found in that stage of its growth would be referred 
to that genus. Subsequently, from impressions on the matrix, the 
shell seems to have straightened out and become an Ancyloceras. 
Two species of Crioceras have been previously recorded. from 
Australia. One is figured and described in Moore’s paper 
referred to. The other is by R. Etheridge, jum, in the Proc. of 
the Royal Physical Society of Edinburgh (loc. cit., p. 43). Mr. 
Moore’s species, 0. australe, will be dealt with presently. Cro 
ceras jackit, Ether, is quite a different shell from ours. The 
ceras from the head of the ders River, as follows — 
gigantic species of Ancyloceras, exceeding the A. gigas ot the Isle of 
Wight in size, and differing by having the transverse ribs large 
forking on the side, and a row of large compressed tuberel 
each side of the back, It most resembles the A. zaberelli of the 
French Lower Greensand. I name it A. flindersii.” I 0 not 
point out that this is entirely different from our species. 
Crioceras australe, Moore, Pl. 10, figs. 5and 6.—I believe that the 
specimen found with the last species is a fragment of the anew 
which is thus described :—* Shell very large, discoidal, W oo 
rounded, incurved, the inner whorls rather closely fitting, ae 
separate. In the younger state, as seen in the reduced pig is 
shell. In the adult shell the ribs become widely separated 
largest. chamber measuring 34 inches at the back, and © 
possess very acute ridges, with two depressed bosses on each rT] 
the depressions between the ribs being regularly oe ae 
block containing the last. five chambers of the shell Jt ih 
compressed on the back, and though it is not compl 
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