139 
bluish lustre ; whorls 3^, rapidly increasing, flattened between 
the periphery and the suture, subangled at the periphery, slightly 
descending at the aperture ; sculpture numerous irregular oblique 
sinuate sharp costas which are smaller and closer on the last 
whorl, in their interstices and parallel to them are close fine hair 
lines, there is a decided break in the sculpture on reaching the 
embryonic whorls which faintly repeat the adult sculpture ; suture 
deep, acutely impressed ; spire sunk, embryonic whorls 1^, distinct; 
epidermis glistening ; base rather flattened, umbilicus about one- 
sixth of major diameter, perspectively exhibiting all the earlier 
whorls ; aperture diagonal, peristome straight, sharp, body whorl 
overlaid by a thin callus. Diam. maj. 16, min. 13, alt. 6 mill. 
Hab. Summit of Mount Ledgbird, 
Jaw (pi. xxi., fig. 6) thin membranous, emarginate on the convex 
margin, projecting on the concave, ends angled, finely transversely 
striate. Radula (pi. xxii., fig. 1) small, strap shaped, three mill, 
long by one broad, rows curving slowly backward (posteriorly 
with relation to the animal), till the marginals are reached, when 
they run straight across the ribbon until the extreme marginals 
which sweep slightly forwards ; formula, 150 rows of 21 : 10:1 : 
10:21 ; the rachidian is small, two-thirds the size of the immediate 
laterals, cusp ovate, extending along three-fourths of the basal 
plate and bearing at half its length two minute accessory cusps ; 
the cusps of the laterals increase in magnitude as they retreat 
from the centre, and are supplied with both distal and proximal 
accessory cusps, the main cusps of the inner laterals fall short of, 
and those of the outer exceed, their basal plates, whose alate 
angle is scarcely expanded ; the outer four laterals are modified 
by transition to the marginal type, whose proximal accessory cusp 
assumes a sabre shape, and increases to nearly the size of the 
main cusp, the extreme marginals offer a short tridentate blade. 
The shell of this species resembles that of It. sinelairi , of 
Tasmania, and before examining the unexpected dentition, I 
quite concurred with Mr. Brazier in referring this species to 
Rhytida. 
var. ball i, Brazier , 1889. 
Illustration. Brazier, Aust. Mus. Mem. 2, pi. 4, figs. 13, 14, 
26, (reversed). 
Type. Australian Museum. 
Shell depressedly globose, often eroded, whorls rounded, spire 
slightly raised, base rounded, umbilicus narrow but exhibiting the 
previous volutions. Diam, maj. 11, min, 10, alt. 6 mill. 
1/ab. Summit of Mount Ledgbird. 
var. ledgbirdi, Brazier , 1889. 
Illustration . Brazier, Aus. Mus. Mem. 2, pi. 4, figs. 19, 20 
(reversed). 
