139 



bluish lustre ; whorls .'J|, rapidly increasing, flattened between 

 the periphery and the suture, subangled at the periphery, slightly 

 descending at the aperture ; sculpture numerous irregular oblique 

 sinuate sharp costae 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 H, distinct ; 

 epidermis glistening ; base rather flattened, uml>ilicus 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. 



Hah. Summit of Mount Ledgbird. 



Jaw (pi. xxi., fig. G) 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 liearing 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 R. sinclairi, of 

 Tasmania, and before examining the unexpected dentition, I 

 quite concurred with Mr. Brazier in referring this species to 

 Rhytida. 



var. BALLi, Brazier, 1889. 



Ilhistration. Brazier, Aust. Mus. Mem. 2, pi. 4, figs. 1.3, 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. 



Hah. Summit of Mount Ledgbird. 



rar. ledgbirdi. Brazier, 1889. 

 Illustration. Brazier, Aus. Mus. Mem. 2, pi. 4, figs. 19, 20 

 (reversed). 



