129 



The specific name is derived from the aboriginal name of the 

 Lower Murray Eiver. 



This minute shell is not the young of JV. Athinsoni, and 

 differs from Leda lucida, T. Woods, by the equality of the 

 transverse diameters of the valves. 



Nucula fenestralis, spec. nov. PI. iv., fig. 4. 



Shell minute, ovate-oblong, somewhat tumid, umbo in the 

 posterior-third ; the shorter posterior side with a rounded 

 margin ; the anterior side roundly truncated. Surface orna- 

 mented by equidistant and equal-sized radial and concentric 

 ribs ; edge of valve crenulated. 



Dimensions. — Length about 2, height about 1^ millimetres. 



Locality. — Table Cape, Tasmania {B. T.) . 



The peculiar feature of this fossil is the subcentral umbo and 

 the gross cancellated sculpture. 



GENUS LEDA. 

 SYNOPSIS OF SPECIES. 



A. Non-rostrated ; ovate-quadrate. L. ololella. 



More circular and depressed. L. planiuscula, 



B. Eostrated. 



Elougately-lanceolate. L. Huttoni. 



Elougately-oval. L. acinaciformis. 

 Ovate-trigonal or pyriform 



G-radually acuminately-rostrated. JL. apiculata. 



Abruptly rostrated and compressed. L. leptorliynclia. 



Oblong-ovate. L. lucida^ 

 Transversely-ovate, posterior side the shorter. L. prcelonga, 

 Eostral prolongation, biangulate. 



Oblong- subovate. T. Woodsii. 



Ovate-trigonal. L. crehricostata. 



Leda obolella, spec. nov. PI. v., figs. 3a— 3^. 



Shell small, thin, ovate-quadrate, slightly inequilateral^ 

 depressed ; umbos very small, slightly recurved, almost central ; 

 dorsal margin regularly sloping, anterior margin roundly 

 truncate, the antero-dorsal area slightly depressed ; posterior 

 margin rounded, surface faintly concentrically striated;, 

 lunuie obsolete ; hinge teeth small, curved, about 15 on each 

 side of a rather broad, erect, triangular cartilage pit. 



Dimensions. — Length, 11 'o ; height, 9'5 ; thickness through 

 both valves, 4 millimetres. 



Localities. — Not uncommon at Muddy Creek ; Schnapper 

 Point ; gastropod bed, Middle Murravian, near Morgan {B.T.). 



This fossil differs from all living species, but has some re- 



