86 Proceedings of the Royal Society of Victoria. 



Description. — Shell very large, trochiform, apical angle about 

 75 degrees, rather lacking in solidity considering its size. 

 Whorls slightly convex, with a well impi'essed suture, earlier 

 whorls rather flat, impressed suture less marked ; whorls rapidly 

 increasing in size, and numbering about nine. The median band 

 is broad, being in width about one-sixth the height of the whorl, 

 it is very strongly marked, and is situated a little below the 

 middle of each whorl. Body-whorl strongly keeled at the base ; 

 base very slightly convex to a well-marked umbilicus, which 

 penetrates only to the penultimate whorl ; aperture subquadrate, 

 posterior portion of the lip thin, lower edge of the lip slightly 

 thickened and rounded off, becoming thicker and more solid 

 towards the columella, the latter being strikingly more solid and 

 robust than the rest of the shell. 



There is evidence of faint spiral striae, irregular in strength, 

 on the upper or posterior portion of the penultimate and body- 

 whorls, and a faint spiral striation is discernible on the base, 

 becoming a little clearer and closer towards the umbilicus ; the 

 general character of the surface-marking being a rude and 

 irregular striation in conformity with the lines of growth, the 

 base also showing a strong irregular undulation parallel to the 

 growth. 



Dimensions. — Basal diameter, 5| inches, or 136 mm.; height 

 from the base, 4^ inches, or 103 mm.; breadth of aperture, 3 

 inches or 75 mm.; depth of aperture, about H inches, or 36 mm.; 

 width of fasciole, near slit, 6 mm. to 5 mm. further back on the 

 body-whorl ; length of slit, 48 mm. 



Locality. — Basal horizon of the Table Cape Beds, Tasmania, in 

 coarse ferruginous grits. Jan Jukian (Eocene). 



Observations. — The large size of this species is worth special 

 note as it compares very favourably with the largest of the 

 specimens yet obtained of P. adansoniana, Crosse and Fischer, 

 the best known of the recent species. The thinness of the shell 

 is rather remarkable, especially in view of the coarse gritty 

 material in which it is preserved, and in this respect it is 

 scarcely as thick as the much smaller species of McCoy, in 

 addition to this feature it differs from P. tertiaria, in its greater 

 apical angle, the more impressed sutures, in its umbilicus, and in 

 its inornate character. The shortness of the slit, and the 



