PELECYPODA 173 



This species is very like the New South Wales genotype, which is similarly truncate 

 posteriorly. 



Mysella alpha, n.sp. (Plate XLVI, fig. 6). 



Shell small, rather thin, white, elongate-oval, very oblique. Inequilateral; anterior 

 end greatly produced. Beaks low, tips small, smooth and globular, situated at about the 

 posterior eighth. Dorsal margin straight and horizontal for a little less than half the 

 length of the shell forward from the beaks, where it is weakly subangled, the margin 

 then descending gradually to a somewhat narrowly rounded anterior end. Posterior end 

 very short and steep, broadly rounded. Both ends curve gradually and regularly into 

 the broadly rounded basal margin. Right valve hinge with two divergent cardinals, 

 separated by the resilium and an anterior lateral lamella, which is parallel to the dorsal 

 edge. Left valve with thickened valve margins one on each side of the resilium ; these 

 interlock with the cardinals and the lamella of the opposite valve. Valve margins smooth, 

 minutely bevelled. Surface smooth, except for faint unequally spaced concentric lines 

 of growth. 



Length 2-15 mm.; height i-6 mm.; thickness (one valve) 0-45 mm. (Holotype). 



Habitat: Off Three Kings Islands, St. 933, 260 m. 



This species is very close to Montaguia charcoti, Lamy (1906, Bull. Mas. Hist. Nat. 

 xii, pi. 1, figs. 13 and 14) described from Graham Land in the Antarctic, and later 

 recorded from Macquarie Island by Hedley 19 16 (Mollusca, Australasian Ant. Exped., 

 iv, p. 32). I have not seen Macquarie Island specimens, but compared with Lamy's 

 excellent figures of the type of the Graham's Land charcoti the Three Kings shells 

 differ only in the lateral lamella being much shorter, the anterior cardinal smaller and 

 the dorsal margin slightly subangled above. 



Mysella beta, n.sp. (Plate XLVI, fig. 7). 



Shell larger than alpha, more solid, oval, but not so elongate. Dorsal margin, anterior 

 to the beaks, broadly arched. Anterior end greatly produced, broadly rounded ; pos- 

 terior end somewhat narrowly rounded. Beaks low, tips small, smooth, depressed, 

 rounded. Valve margins smooth. Surface smooth, except for unequally spaced con- 

 centric lines of growth. Hinge similar to that of alpha. 



Length 3-3 mm.; height 2-8 mm.; thickness (one valve) o-8 mm. (Holotype). 



Habitat: Off Three Kings Islands, St. 933, 260 m. 



This species is close to alpha, but grows larger, is not nearly so obliquely elongate- 

 oval, and has more bluntly rounded beaks. 



Genus Borniola, Iredale, 1924 

 Type (original designation) : Bortiia lepida, Hedley 

 Borniola neozelanica, n.sp. (Plate XLVI I, fig. 8). 



Shell small, thin, white, oblong inequilateral, somewhat compressed, sculptured with 

 densely packed very fine radiate threads, interrupted by well-defined concentric growth 



