128 



bj fine radial threads, which form an open tessellated sculpture.. 

 Umbos sharply incurved; lunule shallow (scarcely defined),, 

 broadly lanceolate ; ligamental pit inconspicuous ; cardinal 

 teeth lamellar, eight on the posterior and about 20 on the 

 anterior slope. Edge of the ventral half of the valves minutely 

 crenulated. 



Dimensions. — Length, 7"5 ; height, 6"5 ; thiclvness through 

 both valves, 4 millimetres. 



Localities. — Table Cape, Tasmania (B. 21. Johnston) ; G-as- 

 tropod bed of the Middle Murravian, near Morgan {B. T.) \ 

 Corio Bay, G-eelong {B. T.). 



The radial sculpture is not always visible by the aid of a 

 pocket-lens, but the crenulated margin and the radial lines 

 which proceed from it towards the interior are always dis- 

 cernible. 



This shell has been wrongly placed in Portlandia, which is a 

 Yoldia having the valves posteriorly closed, whilst it has the 

 simple pallial line and other characters proper to Niccula. 



Nucula semistriata, spec. nov. PI. iv., figs, oa — 56. 



Shell small, obliquely trigonal, moderately depressed ; the 

 very short posterior side roundly truncated ; anteriorly pro- 

 duced and rounded at the extremity. Surface with depressed 

 folds of growth, somewhat retroflexed, the folds increasing in 

 size, and here and there anaslomising, towards the front where 

 the interspaces are conspicuously radially ridged ; posterior 

 and anterior slopes radially striated. Umbos rather elevated, 

 sharply recurved, lunule inconspicuous. Edge of valves crenu- 

 lated. Ligamental pit scarcely defined. 



Dimensions. — Length, 5 "5 ; height, 4'25 ; thickness through 

 both valves, 3 millimetres. 



Localities. — Turritella clays, Blanche Point, Aldinga Bay ; 

 glauconite sands, Adelaide bore {B. T.). 



This species differs from N. Atkinsoni by its greater obli- 

 quity and the thick retroflexed folds. 



NuculaMorundiana, syec. nov. PI. iv., figs. 2a— 26. 



Shell minute, tumid, solid, trigonal, equilateral ; posterior 

 side obscurely angled and flattened above ; anterior side ob- 

 tusely rounded ; umbones obtuse ; surface ornamented with 

 regular, equal rounded, concentric ribs, and microscopic radial 

 striae ; inner margin of valves minutely denticulated. 



Dimensions. — Length and height 3, thickness through both 

 valves 2 millimetres. 



Localities. — Muddy Creek, Hamilton, and the calciferous- 

 sandstones of the Elver Murray-cliffs near Morgan. 



