130 



Locality and Horizon. — The older tertiary of Muddy Creek, 

 Hamilton, Victoria, and the contemporaneous " Upper Murra- 

 vian," near Morgan (North-West Bend), on the Eiver 

 Murray. (Tate.) 



Z. angustata is very much of the shape of Zenatla acinaces, 

 Quoy, recent New Zealand and New South "Wales, hut it is 

 much narrower, more attenuated posteriorly, and the anterior 

 side is rather longer and not so ahruptly arched. Specimens 

 from the Eiver Murray cliffs have thin, fragile, semi-pellucid 

 tests ; whilst those from Muddy Creek are thickish and opaque, 

 and of larger dimensions. Similar differences are found among 

 living species inhabiting the laminarian zone of the compara- 

 tively still waters of land-locked hays, and of the rough waters 

 of the open coast line. 



ON SOME EECENT AND EOSSIL KELLIAD^ EEOM 

 SOUTH AUSTBALIA. 



Lepton ceassum, nov. spec. PI. v., fig. 9. 



Shell thick, transversely oval, moderately convex ; umbo 

 post-median moderately inflated. Surface smooth, but, viewed 

 under the lens, with narrow equidistant sulci and flat plications, 

 punctatedly impressed in the grooves, particularly on the 

 posterior and anterior sides. Anterior and posterior margins 

 rounded, ventral margin nearly straight, dorsal slightly arched. 

 Length - 25, breadth '18 inch. 



In the only valve, a left one, found of this species, there is a 

 small cardinal tooth in front of the small cartilage pit, and the 

 two laterals are elongated and erect. 



Locality and Horizon. — Eiver Murray Cliffs near Morgan 

 .(North-West Bend), Upper Murravian series. 



Lepton PLANirscrLrM, iiov. spec. PL v., fig. 12. 



Shell minute, quadrately ovate, compressed, nearly equi- 

 lateral, posterior side a little the longer ; umbo prominent, 

 acute ; surface marked with strong folds of growth, which are 

 broader and more elevated in the umbonal region, and very 

 finely concentrically striated. 



Eight valve with divergent lateral teeth of equal and mode- 

 rate size, between which is the broadly triangular cartilage pit. 



Dimensions. — Length, - 175 ; breadth, \15 inch. 



Locality and Horizon. — In a sandy layer in the limestones of 

 the Upper Aldinga series (Miocene), on the south side of Port 

 Willunga Jetty. 



This species comes near to L. anstrale, Angas (see p. 13), 

 from which it differs in shape, in being more equilateral, and 



