Art, XVIII. — On the Occurrence of Two Species of 

 Cryptoplax in the Tertiary Rocks of Victoria. 



By T. S. hall, M.A. 



(With Plate XXX.). 

 [Eead 10th November, 1904]. 



The occurrence of two species of Cryptoplax in our Victorian 

 Tertiaries is worthy of notice, as hitherto no fossil representa- 

 tives of the genus have been found. It is, however, in its 

 recent distribution confined to the south-western Pacific, and 

 the southern shores of Australia, and in its existence as a 

 Tertiary fossil in Southern Australia we have but one more 

 more instance of the essentially Australian character of our 

 Cainozoic fauna. 



As regards the age of the two distinct deposits from which the 

 present specimens come, opinions differ. The lower beds of 

 Muddy Creek are by some regarded as eocene and by others as 

 oligocene, while the upper series is generally spoken of as 

 miocene, and was by McCoy considered older pliocene. The 

 question is pei'haps not ripe for settlement, though opposing 

 authorities are equally positive in their views. To avoid the 

 constant confusing references to age made in the incidental 

 description of fossils by authors with divergent opinions, Mr. 

 Pritchard and myself have suggested Barwonian, with two 

 subdivisions, Balcombian and Janjukian, for the older series, 

 and Kalimnan for the younger. 



The genus Cryptoplax is not uncommon in the Kalimnan, but 

 I have seen only one specimen from the Balcombian. 



Cryptoplax ppitchardi, n. sp. (PI. XXX., Figs. 1-6). 



All the specimens of the valves that I have found, thirty in 

 number, are much worn and are polished by attrition like so many 

 of the fossils in the Kalimnan of Muddy Creek, and in very few 

 cases IS the articulamentum distinctly shown. The valves 



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