BY R. TATE AND W. L. MAY. 455 



Marginella Joiinstoni, Petterd. 



This is a micromorph of M. muscfiria, and exhibits a tumidity 

 on the body- whorl near the outer lip as in that species; though 

 on account of smaller size of the shell it is not so conspicuous. 

 Because Messrs. Pritchard k GatlifF considered this feature to be 

 absent, they have maintained M. Johnstoni to be of specific rank. 

 Examples of intermediate size occur on the south coast of Yorke 

 Peninsula, S. Australia. 



Mitromorpha alba, Petterd {Columhella). 



Shell dull white beneath a thin pale straw-coloured epidermis, 

 mitrteform, acuminate at both extremities. Embr3^o of two and 

 one-half smooth convex whorls, of large increase; the tip is of a 

 brown colour. Spire-whorls three and one-half, ornamented by 

 revolving subacute ridges, approximately equal-sized and equi- 

 distant, at first five in number, increasing to eight on the 

 penultimate. Body-whorl about three-fourths the total length, 

 ornamented all over with revolving ridges, which are more 

 rounded than those of the earlier whorls. Aperture narrow; 

 columella very slightly arched, with two oblique plications 

 (developed at the adult stage only); outer lip with a wide and 

 shallow sutural sinus, smooth within but its margin minutely 

 crenulated by the spiral lirae. Length 6, breadth 2.25 mm. 



The form is that of a Conomitra^ but having a sutural sinus 

 and the columellar plaits not continued into the interior ; it 

 simulates Mitrella, differing by the presence of folds on the 

 columella. 



In general terms the description of M. llrata, Adams (the type), 

 applies to the Tasmanian shell, but as neither figure, dimensions, 

 nor details of ornament are given, it would be unsafe to attach 

 the two; though in M. lirata the ^pire and aperture are stated 

 to be of equal length. The original diagnosis is rather contra- 

 dictory in respect to the characters of the columella, thus "recta, 

 leviter transversim lirata;" and "like the Cancilla-ionn oi Mitra, 

 but without any trace of plaits on the columella," and again 



