319 



Umbilicus simple, open ; shell globulose (Naticixa). 

 Surface sculptured. 



Surface grooved ; shell solid. 11. arata. 



Ornament of spiral wavy threads ; shell thin. 



12. limata. 

 Surface smooth, or nearly so. 



Suture canaliculate, umbilicus small, not margined. 



13. ^jo/iVrt. 

 Suture impressed ; umbilicus wide, margined ; body- 



wliorl inflated. 14. persjyectira. 



Suture linear ; umbilicus small, not margined. 



15. Aldingensis. 



Umbilicus simple, very large ; shell depressed, auriform 



(SntARETOPSIS). 16. siihinfunclihuhun. 



1. Natiea Hamiltonensis, Tate. PL x., fig. 6. 



N. Wintlei, var. Hamiltonensis, Tenison-Woods, Proc. Lin. 

 Soc, K.S.W., v(.l. III., p. 229, tab. 21, fig. 8, 1878. 



Shell globulose, fragile ; spire short ; whorls four and a-half. 

 <jf very rapid increase, smooth or faintly wrinkled around suture : 

 af)ical whorl flat, the others rotund, more abruptly sloping to the 

 posterior suture ; suture linear. 



Aperture broadly oval, slightly (jljlique, outer and basal mar- 

 gins acute ; columella slightly arched, thin, joined to the outer 

 lip by a thin callus : umbilicus narrow, with a not very 

 prominent funiculus, which is defined in front Ijy a narrow 

 groove, but the umbilicus is broader and deep behind it. 



Dimensions of a large specimen : — Length, 20 ; width, 19 : 

 \-ertical height of aperture, 15 ; radius of aperture, 11 ; width of 

 umbilicus, 2. 



Localities. — -Eocexe — ^Muddy Creek (very connnon) I ; Morn- 

 ington I ; Bird-rock Bluff (rare) I ; Cheltenham ! ; Gellibrand 

 River ! ; Fyansford I ; Turritella-beds, Aldinga Clifl's and Ade- 

 laide-bore ! ; River Murra}' Cliffs ! Miocene — Kalima, Gijjps- 

 land Lakes (rare) ! 



Rem^arks. — Tenison-Woods w^as acquainted with only im- 

 mature examples (about 4 ram. diameter) of this species, which 

 he referred under a varietal name to his N. Wintlei. In the 

 adult stage, such as I have illustrated, the differences indicated 

 between it and N. Wintlei are more accentuated. N. Hamilton- 

 ensis is a fragile shell, with a shorter spire and more convex 

 whorls, whilst the aVjsence of a callus on the posterior part of 

 the columella is a very conspicuous feature. 



Among living species with which I have compared it, it makes 

 the nearest approach to N. Zealandica, Q. k G., but differs by 

 more inflated spire-whorls and slender funiculus. 



