494: MOLLUSCA OF MAST HEAD REEF, QUEENSLAND, II., 



wrinkled towards the suture and ornamented throughout by fine 

 close radial hair-lines. Base slightly concave, the plane of the 

 periphery continued in the aperture, a small umbilicus corres- 

 ponding to the spire. Aperture horizontal-oblong, adnate to the 

 keel, thickened externally. Major diam. 2-25mm.; minor diam. 

 1-6 mm.; height 0-9 mm. 



This species, common in 17-20 fathoms around Mast Head, 

 represents a genus new to Australia. The Chinese M. morleti 

 Fischer,"^' closely resembles it, but, judging from literature, differs 

 in sculpture, and especially by the denticulate periphery. 



RissoA NOVARENSis Frauenfeld. 



Alvania novarensis Frauenfeld, Novara Moll, p.ll, pi. ii. fig. 16 

 (1867). Rissoa {Alvania) trajectus Watson, Chall. Exped. Zool. 

 XV. 1886, pl.xliv. fig. 6. 



This synonymy has not been previously noted, but B. trajectus 

 appears to be embraced within the limits of variation of R. 

 novarensis. The species thus develops a continuous range from 

 Sydney to the Gulf of Carpentaria. 



Rissoa liddelliana, n.sp. 



(Plate xvii., fig.24.) 



Shell minute, thin, translucent, conical, perforate. Whorls 

 four, rounded. Colour white. Sculpture: the first two whorls 

 are smooth, the others ornamented by elevate lamellae which 

 continue across the suture and traverse the whole whorl. On 

 the body-whorl they amount to seventeen, are prominently angled 

 at the shoulder, less so at the base. The interstices are broad 

 and flat, traversed by regular dense spiral microscopic scratches. 

 Aperture perpendicular, circular, entire, almost, but not quite, 

 free from the body-whorl, fortified by a broad and thick varix. 

 Umbilicus a small axial furrow. Height 1*25 mm.; breadth 

 0-8 mm. 



* Fischer, Journ. de Conch, xxv. 1877, p. 202, pi. iv., fig.l; and Melvill, 

 Proc. Malacol. Soc. vii. 1906, p. 27. 



