306 Proceedings of the Royal Physical Society. 



Careful examination into the history and literature of this 

 genus of Cephalopoda has failed to discover any species 

 to which I can refer the Australian form, but the nearest 

 species appears to be the IsTeocomion, Crioceras Duvalleii 

 (L'Eveille). The whorls in the latter are more open and not 

 so contiguous as in C. Jackii, and the tubercles or spines 

 are finer and much more slender in the French and British 

 species. 



The Cretaceous rocks of Australia have as yet only yielded 

 one species of Crioceras, described by Mr C. Moore, F.G.S., as 

 C. Australe, from the Upper Maranoa district.* The deep 

 sulci separating the costse or ribs will at once distinguish this 

 from our C. Jackii, in which the former are very much re- 

 duced in their dimensions from the contiguity of the latter ; 

 neither are the ridges acute but well rounded in C. Jackii ; 

 and lastly, Mr Moore describes only two bosses in his species 

 on each side. 



The allied genus Ancyloceras is also represented in the 

 Cretaceous beds of Queensland by one species, A. Flindersi 

 (M'Coy), and briefly described -f by Professor M'Coy as long 

 ago as 1867. It is stated to be allied to the French Cretace- 

 ous species A. Tabarelli (Astier) ; and even supposing the 

 form now under discussion to be an Ancyloceras rather than 

 a Crioceras, as has been suggested to me by Dr Woodward, it 

 cannot be this species. The British Museum Collection con- 

 tains the " Astier Collection," and having compared it with 

 the type of A. Tabarelli, I can safely affirm that it has not the 

 slightest connection with the latter. Under the name of 

 Crioceras Jackii T have included two shells, which at first 

 sight appear to differ from one another in certain particulars ; 

 but I think they are merely forms of the same species. In 

 the more robust of the two (fig. 55) the six rows of tubercles 

 are continuous along the greater part of the largest whorl, 

 the dorsal pair being quite so. In the second specimen (fig. 

 58), on the other hand, there are no tubercles at all visible 

 on the body whorl, and they are only perceptible on the inner 

 whorls when separated. The other characters of the two 



* Quart. Jour. Geol. Soc, xxvi., p. 257. 

 + Annals Nat. Hist,, 1867, xix., p. 356. 



