PELECYPODA 165 



Aupouria parvula, n.sp. (Plate XLV, fig. 1). 



Shell minute, solid, valves only slightly convex, suborbicular, inequilateral, beaks at 

 about the posterior third. Anterior end broadly rounded, produced. Posterior end 

 truncated medially, causing a weak subangle with the basal margin. Prodissoconch 

 large, capped by a rounded boss and marked off by a thin bounding rim. Sculpture of 

 numerous indistinct and somewhat irregular concentric growth lines. Hinge plate 

 broad, arcuate. Resilium pit deep, shaped like an inverted U ; on either side of it a 

 vertically striated ligamental area, and below, upon the anterior distal portion of the 

 hinge plate only, there are two short transverse rather strong teeth, which interlock with 

 a pair of similar teeth in the opposite valve. Muscle scars oval, deeply impressed, pallial 

 line simple. Colour white. 



Length i-6 mm. ; height 1-5 mm. ; thickness (one valve) 0-4 mm. (Holotype). 



Habitat: Off Three Kings Islands, Sts. 933, 934, 260 m. 



Thiele's Limopsilla (1923, Zool. Anzeiger, lv, Nos. 11-13, p. 289) proposed for 

 Limopsis pumilio, Smith, is not applicable to the species here described. While there is 

 a certain similarity in shape, and a correspondingly small size, the hinge details of the 

 two are irreconcilably diverse, that of pumilio being particularly strong and massive for 

 the size of the shell. 



Family PHILOBRYIDAE 



Genus Cosa, Finlay, 1926 



Type (original designation) : Hochstetteria costata, Bernard 



Cosa serratocostata dispar, n.subsp. (Plate XLV, fig. 7). 



Shell small, rhomboidal, solid, moderately inflated. Colour uniformly buff. Prodisso- 

 conch typical. Anterior margin vertical, dorsal margin horizontal, posterior margin 

 almost vertical, ventral margin broadly rounded. Sculpture of fourteen radial ribs 

 which in relative strength fall into two series, there being seven massive radials over the 

 middle area of the shell, the remaining three anterior and four posterior radials being 

 of considerably weaker development. These radials are bold and triangular in section 

 with interstices at the margin wider than the diameter of the ribs. The whole shell is 

 crossed by narrow closely spaced concentric ridges, which imbricate the radials where 

 they surmount them. Ventral margin strongly denticulated by the radial ribbing. 

 Hinge plate narrow and long, chondrophore and vertically grooved extremities of hinge 

 plate typical. 



Height 2-2 mm.; diameter 2-1 mm.; thickness (one valve) 0-9 mm. (Holotype). 



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



This is a readily separated variant of serratocostata (described from shell sand from 

 Tom Bowling Bay) which is characterized by the unequal development of its radials, 

 seven of them over the middle of the shell being disproportionately large. The inter- 

 costal spaces also are proportionately wider than in the typical species. Both serrato- 



