100 



Rissoia ( Amphithalamus) Simsoni, spec. nov. 



Pupiform, strong, shining, white, tinted with pale-chestnut.- 

 Whorls four, flatly convex, sculptured with microscopic oblique 

 striae ; suture linear. Apex hemispheric of one and a-half 

 whorls. Last whorl somewhat flattened on the ventral face. 

 Aperture oval; peristome continuous, adnate to the parietal 

 wall. Resembles R. dissimilis on a large scale. 



Length, 4*5 ; width, 1-5 mm. 



Species-name in compliment to our friend and co-worker, Mr. 

 Auguste Simson of Launceston. 



Derwent Estuary, Tasmania (W. L. May); also Port Fairy, 

 Victoria (Rev. T. Whan /). 



Rissoia (Cingula) rubieunda, spec. nov. 



Shell minute, elevated conic, imperforate, moderately thick; 

 varies in colour from pellucid-brown to opaque- white. 



Pullus obtuse, of one and a-half turns. Spire-whorls four, 

 moderately convex, widest near the anterior suture (some 

 examples show a tendency to imbrication), smooth, and sculptured 

 with growth-lines. Suture linear, distinct. Last whorl rather 

 depressed at the suture, rounded at the periphery, a little con- 

 tracted at the outer lip. 



Aperture rotund, chestnut-coloured in the interior ; peristome 

 entire ; outer lip thin ; columella lip slightly exsert, margining a 

 false umbilical chink. 



Length, 2*5; width, 1-0 mm. 



Derwent Estuary, Tasmania (W. L. May); many examples. 



This may prove to belong to Hydrobia, when the animal has 

 been studied. 



R. perexigua, nom mutand. 



Rissoia minutissima, Ten. -Woods, P.R.S. Tasm., 1878, p. 122 

 non Rissoia minutissima, Michelin, " Gen. Rissoia." 



Rissoia (Nodulus) pellucida, spec. nov. 



Shell minute, obliquely oval, somewhat stout, translucent-white, 

 smooth, shining, imperforate. Pullus small, obtuse. Spire- 

 whorls three and a-half, rapidly increasing, slantingly convex, 

 without visible ornament or sculpture. Aperture roundly oval ;. 

 peristome thick, continuous. 



Length, 1*2 ; width, *75 mm. 



Frederick Henry Bay, Tasmania ( W. L. May). 



This species differs from other members of the section by its 

 Littorina-like shape ; however, the following species in Section 

 Cingulina offer some comparisons : — It has the outline of 

 R. hyalina, which possesses spiral raised striae and delicate- 

 growth-lines, and it is more obliquely oval than R. littorinceformis.. 



