92 



summit ; slightly arched, narrow, of nearly equal width till it 

 slightly widens at the everted front. Outer lip thickened and 

 well-margined all round, smooth within. Columella with one 

 strong oblique plait at the front, which is succeeded on the pillar 

 by seven transverse thread-like plaits ; the columella-plait runs 

 out to form the left margin of a shallow and wide effuse notch. 



Length, 1*6 : width, -95 mm. 



Tasmania, W. F. Petterd!. 



This species much resembles If. Isseli, Nevill (31. nympha, 

 Braz.), but it has more plications, and the outer lip is smooth ; from 

 M. cymbalum, which is a much larger shell, it is more narrowed 

 anteriorly, and the plications of a different type. M. Hallii is 

 truncated at the apex. M. alternans appears to resemble it, and 

 though they have the same number of plications, yet their dispo- 

 sitions are so distinctly different that we must regard them, in 

 the absence of actual comparisons, as distinct. 



Marginella biplieata, spec. nov. 



Shell small, cylindroid, pellucid, straw-coloured. Spire very 

 obtuse, of three and a-half whorls, scarcely exserted. Aperture 

 narrow elongate, widening to the front, obtuse-angled posteriorly. 

 Outer lip scarcely thickened : not ascending on the spire, its 

 junction marked by a slight retiring angle ; smooth on the inner 

 side. Columella with two strong oblique plaits at the front — 

 the posterior one is slightly the stronger ; anterior emargination 

 well-defined. 



Total length, 4 ; greatest width, 2 mm. 



Port Esperance, Tasmania ; in 24 fathoms, 2 exs. ( IT. L. May). 



It is nearest to M. Stanislas, but is shorter and relatively 

 broader, and the apex is more obtuse, whilst the most prominent 

 differences are in the smooth inner lip and biplicated columella. 



Mapginella Simsoni, spec. nov. 



M. denticulata (pars), Tate, non Conrad. 



M. minima, Petterd, non Sowerby. 



Shell pyriform, contracted in front, shining, white. Spire 

 immersed, though not wholly concealed. Aperture as long as the 

 shell, slightly everted in the young. Outer lip thickened, smooth. 

 Columella with about ten plications, decreasing gradually in size 

 from the front. 



Length, 1*9; greatest width, 1*3 mm. 



Tasmania and South Australia. 



M. minima, Petterd, the type of which we have studied has a 

 length of 1/4 and a breadth of 1/0 mm., and besides being smaller 

 than M. denticulata it is slightly more attenuated to the front, 

 and the outer lip is not thickened ; differences which may be 

 attributed to a young age. 



