259 



Description of the Fossiliferotjs Bed. 



Recently my attention has been directed to a new locality 

 for the occurrence of beds of this age situated near the 

 Mount Mary railway station, on the Adelaide to Morgan line. 

 At a distance of one and a half miles from the railway station, 

 towards Morgan, at the 9 If mile post, the line passes through 

 two shallow cuttings, at the summit of a slight rise in the 

 grade. The section exposed in these cuttings shows a maxi- 

 mum face of 7 feet, the lower 5 feet consisting of a shelly 

 deposit, which latter is capped by layers of travertine lime- 

 stone having: an average thickness of 2 feet. 



The shell-bed (so far as seen) consists entirely of oysters, 

 and is apparently limited to one species, Ostrea sturtiana. 

 These are in enormous numbers, being packed closely together, 

 and with only a slight amount of inorganic bed material, 

 the latter consisting of calcareous sand and shelly fragments. 

 The occurrence of paired valves was found to be relatively 

 rare, for whilst a few of these were obtained, by far the 

 greater number occurred as separates, probably separated and 

 distributed by wave action. 



The only other organic remains that came under observa- 

 tion were gathered from the washed material obtained from 

 within and around the shells. These were microzoic, and 

 consisted of two species of foraminifera (Rotalia beccarii and 

 Foh/stomella crispa), one or two valves of ostracods, and a 

 fair number of fragments of small spines belonging to 

 Spatangoid echinoderms. 



The facies of the bed and its contents show a direct 

 resemblance to the upper series of the River Murray cliffs, in 

 which 0. sturtiana is the typical and most-abundant fossil. 

 Tate says (3) : — "This species constitutes banks up to- 10 feet 

 or more in thickness in the upper part of the River Murray 

 cliffs, from Overland Corner to beyond Blanchetown." I 

 cannot find that Tate has given any other record for the 

 occurrence of the species than that of the River Murray 

 cliffs, and this is the only locality given by Dennant in his 

 Catalogue. < 4 ) I have collected one or two examples at 

 Hallett's Cove, but it is not known elsewhere in South Aus- 

 tralia, and has not been noted outside of the State. 



The restricted occurrence of this species, as compared 

 with the countless number of individuals assembled within a 

 limited area, is very remarkable when viewed in relation to 

 geographical distribution, and is very difficult to explain. 

 This particular oyster appears to have held the ground of a 



j2 



(3) Trans, and Proc. Roy. Soc. S. Aus., vol. viii. (1886), p. 97 



(4) Records Geolog. Sur. of Victoria, vol. i., pt. ii., 1903. 



