125 



This Australian fossil Septifer proves to be distinct from its-' 

 congeners. So far as I have been able to make comparisons, it 

 approaches S. denticulahcs, Lamk., but differs in its high, 

 rounded umbonal ridge and its latticed ornament. 



GENUS MODIOLAKIA. 

 SYNOPSIS OF SPECIES. 



Shell obliquely ovate-oblong. M. singiclaris. 



Shell oblong, very inflated, acutely truncated behind. 



M. arcacea^ 

 Shell oblong, moderately inflated, roundly truncated. 



Depressed anterior area without rays. M. semigranosa. 

 Depressed anterior area with twelve acute ribs. 



M. Corioensis^ 

 Modiolaria singularis, spec. nov. PI. iii., fig. 7. 

 Shell obliquely ovate-oblong, equivalve, inequilateral, thin,, 

 translucent; umbos large, obtuse, approximate, a little 

 anterior. Surface finely concentrically striated ; umbonal 

 ridge obscurely radially lined. Hinge line crenulated, rest of 

 inner margin plain, except post-ventrally, where it is thickened 

 and crenulated, the crenulations corresponding with the radial 

 lilies, which are more conspicuous internally than externally. 



Dimensions. — Leugth, 2"5 ; height, 3; thickness through both 

 valves, 3 millimetres. 



Locality. — Muddy Creek, a single perfect shell {B. T.). 

 Though, the form approximates to Crenella, yet as the hinge- 

 characters are proper to Modiolaria.^ I prefer to place it there^ 

 despite its abnormal shape and ornamentation. 



Modiolaria arcacea, spec. nov. PI. ix., figs. 2a— 26. 



Shell oblong, umbos marginal, very inflated, iocurved, some- 

 what wide apart; anterior margin rounded, obliquely trun- 

 cated posteriorly, dorsal line slightly arched; posterior area- 

 flattened, defined by a prominent umbonal ridge. Anterior 

 radial area narrow, ribs rounded, crossed by lamellae ; pos- 

 terior radial area extending over the umbonal ridge, rayed 

 with flat ribs about as wide as the depressed interspaces, the- 

 whole crossed by equidistant lamellae. 



Dimensions. — Length, 27 ; height, 12 ; thickness througb both 

 valves, 18 millimetres. 



Locality. — Turritella grits at Ardrossan (O. Tepper). 



Modiolaria semigranosa, spec. nov. PI. iii., fig. 5. 

 Shell oval-oblong, sub-diaphanous ; umbo sub-marginal^ 

 rather depressed ; anterior radial area obsolete, posterior 

 radial area with sub-acute ribs about as broad as the inter- 



