327 



16. Natiea subinfundibulum, spfc. noi: pi. x., tig. ii ; pi. vi., rig. 6. 



Shell usually rather thin, depressed, auriform ; spire very 

 short, obtuse ; whorls three, suture concealed. Surface with 

 crowded, curved, transverse lines, which coalesce at the suture in 

 slight folds. Spiral lines distant and faint, two or three less 

 indistinct at the suture. Aperture obliquely lunate, outer and 

 basal margins acute ; columella nearly vertical, the posterior-half 

 somewhat thickened, slightly reflected, and joined to the outer 

 lip. Umbilicus very large and perspective ; columella-wall of 

 the umbilicus slightly concave, or with an ill-defined medial 

 ridge, distantly spirally-lined and axially closely striate. The 

 edge of the umbilical depression either slopes gradually inwards 

 or is abruptly defined. 



Dimensions. — Length and width, 13 ; height, 8 ; l^asal length 

 of aperture, 12 ; width of umbilicus, 4-5. 



Localities. — Eocene: Muddy Creek I; Mornington! Gellibrand 

 River ! ; Fyansford ! ; Cheltenham ! ; Murray - river Clif!!s !. 

 Miocene : Muddy Creek ! ; Gippsland !. 



Affinities. — This third sjDecies of the section Sigaretopsis, estab- 

 lished by Cossmann (Soc. Roy. Malac. Belgique, vol. XXIIT., p. 

 168, 1888) differs, by comparison of actual specimens, from 

 -V^. in/undibulum, AVat., by narrower and more convex body- 

 whorl, and by more obtuse spire. Deshayes' figures of ^Y. Woodi 

 represent a more globulose shell, with a much-less open umbilicus. 



I would place in this section Xatica umhilicata, Quoy and 

 Gaimard, recent on the coast oi Southern Australia, which is 

 referred to Momilla by Tryon. Our fossil species is more com- 

 pressed and vaulted, and has a much wider umbilicus. 



Varieties. — Var. crassa is distinguished simply l)y its thick 

 test and usually larger size, attaining to 20 mm. in length and 

 width. It occurs at Muddy Creek in the lower and upper beds ; 

 sometimes as a derived fossil, though rarely in situ, in the latter ; 

 also at Cheltenham, where the largest specimens occur. Var. 

 RiiYSA, in which the spiral ornament consists of close-set wavy 

 threads. A single example from the River ^lurray Cliffs. But 

 some specimens of car. crassa from Muddy Creek exhibit this 

 ornamentation in a less conspicuous way, graduating to the typical 

 form in which it is obsolete. 



G ENus Ampullina. 

 Section Euspira. 



Ampullina effusa, v>"'. nor. Pi. x., rigs. 2, -la. 

 Shell acuminately globose, elongate; test thin and fragile; 

 w^horls eiglit and a-half, convex, slightly ilnttened in front of 

 suture ; suture simple, linearly impressed ; spire elongate. 



