323 



Whorls five and a-half to six, suture linear : spire obtuse,, 

 elongate ; whorls rounded, slightly flatted j^osteriorly ; one 

 and a-half apical whorls depressed. Surface with fine growth- 

 lines and coincident stride ; faintly and distantly spirally-lined, 

 especially on the base ; spirally striate on the depressed area in 

 front of the suture. Aperture lunately-oval slightly oblique; 

 outer lip acute not sinuate, basal lip incrassated. Umbilicus 

 wdth a funicular rib ; columella, posterior to the funicle, slightly 

 dilated and confluent with the funicular termination, otherwise 

 the umbilicus is narrow. 



Dimensions of a moderately large specimen : — Length, 25 '5 ; 

 breadth, 21 ; vertical height of aperture, 18 ; radius of aperture, 

 10 ; diameter of umbilicus, 3. The proportion of the height to- 

 the breadth varies between 100 to 80 and 100 to 82 ; but a few- 

 examples from Table Cape have the relative values 100 and 84. 



Localities. — Eocene ; Crassatella-beds, Table Cape (common) I ; 

 basal beds of the Bird Rock-bluff, Hpring Creek (abundant and 

 large) 1 . 



9. Natiea Mooraboolensis, ^pec. nor. PI. vi., tig. 5. 



.Shell globose, solid, smooth ; whorls five ; apex small, pointed ; 

 penultimate whorl flatly convex in posterior two-thirds, some- 

 what jDrecipitously arching to the anterior suture, w^hich is con- 

 cealed ; last whorl very ventricose, slantingly flattened behind. 

 Aperture semilunate ; columella stout, largely expanded behind 

 the umbilicus, which is of moderate width, apparently simple and 

 shallow\ 



Dimensions. — Length, 28; breadth, 27"5v; width of umbilicus, 5. 



Locality. — Eocene subcrystalline limestone on the Moorabool- 

 river, near Geelong (one example by Mr. G. Sweet). 



This species is related to iV. suhstolida, but has a more 

 elevated spire, with the whorls flatly sloping behind. Among 

 living shells it most nearly resembles X. phmihea, but is more 

 globose, whorls flattened behind, shorter spire, and larger 

 umbilicus. 



10. Natiea substolida, >^pec. nor. Pi. vi., fig. 3. 



Shell solid, oval-globulose, subsphierical; spire conoid, very 

 short, apex obtuse ; whorls four narrow, thinly overlapping at 

 the suture ; body-whorl very large and convex. Surface smooth 

 and shining, faintly lined and striated spirally, more conspicu- 

 ously so on the base, crossed by slightly sigmoid incised lines and 

 obscure threads, which at the suture give rise to a narrow 

 wrinkled -band. 



Aperture oblique, regularly semilunate ; outer lip acute, 

 slightly insinuated posteriorly ; umbilicus simple : columella 

 thick, largely expanding above the umbilicus to form a thick 

 depressed callosity. 

 w 



