2 Transactions of the Society. 



Fisher's Creek waters), sandstones composed almost entirely of the 

 fibrous shelly matter of Inoceramus are seen to rest on hardened 

 black slates and Lydian stone. Indeed, in several places, notably 

 near Marathon, I noted the presence of beds almost entirely com- 

 posed of this fibrous material, sufficient to attest that this mollusc 

 must have lived in almost incredible numbers." 



In the same work, p. 463, Mr. R. Etheridge, jun., in referring to 

 the second of the occurrences noted by Mr. Jack, says : — " Speci- 

 mens of an argillaceous limestone have been obtained, with the 

 weathered surfaces covered with white spicular or needle-shaped 

 bodies, which are nothing more than the broken-up prisms of the 

 shell-structure of Inoceramus." These quotations will serve to show 

 the relatively great abundance of Inoceramus in the North Queens- 

 land Cretaceous series. 



The hand specimens of Inoceramus limestone which form the 

 subject of the following notes, came from the Lower Cretaceous 

 beds 63 miles north of Longreacb, Queensland : a locality more than 

 250 miles to the south of those mentioned by Messrs. Jack and 

 Etheridge. These rock specimens were presented to the National 

 Museum, Melbourne, by Mr. John Williams. 



Megascopic Structure. — The rock is of a pink to pale chocolate- 

 brown colour, weathering to ochreous yellow. On fractured sur- 

 faces it appears of a deep reddish brown. The exposed surfaces are 

 densely covered with the spiculiform prisms of the thick outer layer 

 of Inoceramus shells ; and these form so important an ingredient 

 of the limestone as to whiten the weathered surface. Mr. II. H. 

 Walcott, E.G.S., of the National Museum, lias kindly examined the 

 rock in regard to the proportion of carbonate of lime in it — largely 

 due to the presence of these shell-prisms — and he finds this to 

 amount to as much as 60 p.c. This proportion to the bulk of 

 the rock approaches that in a. sample of Totternhoe stone, in the 

 Grey or Lower Chalk of England, in which Mr. Win. Hill * found 

 the prisms of Inoceramus shell to constitute at least 60 to 70 p.c. 

 of the mass. The presence of these prisms in the Queensland 

 rock is, however, rendered more striking than in the English 

 Grey Chalk by the dark colour of the matrix. On the edge of a 

 vertical fracture, or joint-plane passing through the plane of bed- 

 ding, the shell-prisms are seen to be disposed generally with their 

 longer axes parallel with the bedding plane. These lines of sedi- 

 mentation are so distinctly marked by the prisms as to demonstrate 

 very beautifully the false bedding which is typical of this rock. 

 Here and there on the weathered surface fragments of Inoceramus 

 shells may also be seen conspicuously standing out in quadrangular 

 outline, measuring from about 3-7 mm. on the side : these measure- 



* See Cretaceous Rocks of Britain, ii. Lower and Middle Chalk of England. 

 Jukes-Browne and Hill, 1003, p. 300. 



