460 CENSUS OF THE MARINE MOLLUSCA OF TASMANIA, 



Rissopsis spp. — We have referred to this germs three Rissoia- 

 like species which offer two well-defined differential characters, 

 namely, an included nucleus (the summit of the spire is truncated 

 and the nuclear whorls are immersed) and a thin exse-rted 

 columellar lip; in shape they are inclined to be c3dindroid. The 

 reference to Rlssopsis is conjectural, as no authenticated examj^le 

 of it has been studied by us. 



LlOTIA ANNULATA AND L. COMPACTA. 



These are distinct species; the former has a sunken spire and 

 the interspaces between the ribs are smooth; the latter has a flat 

 spire and is spirally striated between the ribs; otherwise they are 

 much alike. 



Cantharidus Allporti, Ten.-Woods {Zizypliinus). 



Living examples are of a shining pale brown colour, sparsely 

 rose-spotted; the lirae within the aperture correspond in number 

 with the exterior revolving ridges. In old specimens the anterior 

 suture is margined by a bifid non-granulose encircling rib. 



Cantharidus Baudini, Fischer {Trochus). 



The so-called Zizyphinus fragum of previous Tasmanian lists 

 is referred to the above. The most conspicuous difference between 

 Z. fragum, Phil., and C. Baudini is in the number of granular 

 ribs: for the former four (apud Philippi), for the latter eight 

 (apud Fischer), increasing to eleven. 



Akera Tasmanica, Beddome. 



Shell globosely-oblong, imperforate, thin, hyaline. Colour 

 brown, darker-tinted posteriorly, with a narrow white band near 

 the shoulder and a wider one in the anterior-third. Last whorl 

 inflated, equalling the total length of the shell, rounded at the 

 shoulder; spire truncated, flush with the posterior margin of the 

 last whorl, separated by a channelled suture, terminated by a 

 hyaline bulbous nucleus. Aperture contracted above, enlarging 

 anteriorly to the arched front; outer lip truncatedly angled pos- 

 teriorly; columella arched, simple. Leugth 1-9, width 1*2 mm. 



