110 



The left valve is invariably concentrically striated, tlie in- 

 terior ribs shoving as faint dark lines, but may present a. 

 smoothed surface from exfoliation of the external sbell layer. 

 Ears very unequal, posterior the larger, aliiform, distantly 

 arcuate-ridged and faintly rayed ; anterior triangular, concen- 

 trically striated. 



Dimensions of a large specimen. — Length, 10; height, 9"5 

 millimetres. 



Localities. — Abundant in the Turritella-marls, Aldinga Bay; 

 glauconitic sands, Adelaide bore ; Muddy Creek, Vict. ; gas- 

 tropod bed, E. Murray cliffs. 



Table Cape, Tasmania {R. M. Johnston!). 



Several stations of the Ototara G-roup, New Zealand 

 (^Hittton, op. cit.). 



Zittel's figures represent the interior with ten ribs ; Hutton, 

 however, describes the interior with eleven ribs, and the ex- 

 terior as smooth. Nevertheless, two impressions of right 

 valves from AVaihao Eiver in my possession, received from the 

 Wellington Museum, show distinct traces of a fenestrated 

 ornament between eleven radial lines indicating the internal 

 ribs. I think it is clear that Huttou's diagnosis is based upon 

 an excorticated specimen of a left valve, and that the Waihao 

 Kiver specimens here referred to supply the desiderated 

 characters necessary to establish specific identity between 

 the very perfect Australian specimens and those on which 

 P. Zitteli has been founded. 



In respect to P. Atkinsoni, Johnston, a left valve of which in 

 my possession, kindly communicated by the describer, is in 

 every respect identical with Australian specimens, I am in- 

 clined to the opinion that the dissimilar ornament of the right 

 valve has escaped his notice, and I have little hesitation in 

 referring it to P. Zitteli. 



]t is only at Aldinga and Adelaide that are found examples 

 of large dimensions equalling those of the New Zealand ones. 

 The Table Cape and Muddy Creek specimens are usually less 

 than half the size. 



P. Zitteli recalls P. ijersonatns, Zieten, of the Lower Jurassie 

 rocks of Europe ; the Tertiary, P. pygmcBus, Munster, seems 

 to belong to the same type, which is unrepresented in living 

 creation. 



Hinnites Gorioensis, McCoy. 



Itef. — Prodromus Palaeontology of Victoria. Decade VI. ^ 

 pi. Iviii. ; 1879. 



Localities. — Victoria — Extremely common at Corio Bay ; 

 near Bairnsdale, on the Nicholson Biver {McCoy). South 

 Australia — Griauconitic limestone of Aldinga Bay. 



