118 Annals of the South African Museum. 



contains 4 smaller shells collected by Strange at Moreton Bay. 

 They are a slender form of xantho stoma, and show that it is a 

 variable species. 



The following description is from one of the Adams' Type set. 



Shell acuminate-ovate, imperforate, not very solid, apparently 

 somewhat beach-rolled, pale brown. Spire rather short, with nearly 

 straight sides ; apex very sharp, slightly produced. Whorls 5, 

 rapidly increasing, the apical smooth and glossy, remainder marked 

 with occasional faint, almost invisible striation in the lines of 

 growth. Suture very shallow. Aperture a little longer than spire, 

 ovate, base rounded, apex acuminate, outer lip sharp, simple ; 

 columella thickened, furnished with three white plaits ; the iipper- 

 most linguiform larger and further, in proportion, from the others ; 

 the second, straight and much shorter, about half-way between the 

 foregoing and the base of the columella ; while the third, close 

 below the second, is merely a small projection. 



Long. 9-8 ; lat. 6-0 ; apert. 6'1 X 2-5 ; last whorl 8-6 mm. 



There is an appearance of a faint interior rib, parallel to and just 

 inside the outer lip, but this is probably an accident, due to the 

 thinness of the edge of the lip owing to the shell not being quite 

 mature, rather than a characteristic feature. 



Animal unknown. 



Hah. East and South Coasts of Australia ; Tasmania. 



Type in British Museum. 



The typical form of xanthostonia is, in itself, on the extreme 

 borderland of Marinula, having flatter whorls and a more acuminate 

 spire than any of the preceding species ; but in almost any large 

 series intermediates may be found, which link it insolubly to the 

 more normal form described by Swainson under the name of solida. 



The latter differs markedly from the Adams' Types in its more 

 elongate and convex spire and rather more pronounced upper tooth. 

 It may be regarded, on the whole, as representing the southern 

 form of xanthostonia, which appears to undergo a gradual transition 

 in shape between its extreme limits of geographical distribution ; but 

 as neither form is constant, even among specimens from the same 

 locality, and as solida is by no means an appropriate name for a 

 form which is in reality less solid than the Type, it appears in- 

 advisable to perpetuate it. 



So far as I have been enabled to examine specimens from different 

 localities, the typical form, as well as Pfeiffer's slender var. /3, hail 

 from Moreton Bay, Queensland : the extreme form of Swainson's so- 

 called solida is in the great majority in sets from Flinders Island 



