MOLLUSCA— HEDLEY. 



99 



Myrt.'Ea bractea, sp. nov. 

 (Plate xvii., figs. 5, 6, 7, 8.) 



Shell rather solid, moderately convex, flatter in the young 

 stages and becoming more inflated when adolescent, squarely 

 oblong, subequilateral. Colour cream. No radial sculpture. 

 Ribs strong, elevate, varying in number and disposition, 

 usually about fifty and set their breadth apart, spaced medially 

 crowded anteriorly and posteriorly. An occasional rib pro- 

 jects at the edge of the lunule and escutcheon, thus forming 

 a dorsal crest of imbricating scales. Umbo small, prominent. 

 Lunule narrow, excavate, chiefly developed in the left valve. 

 Two cardinals in the left valve. Margins of the valve entire. 

 Length io'5, height 9*5, depth of single valve 2*5 mm. 



This species is near M. bra;:ieri, Sowerby,! but larger, 

 rounder, more inflated and more densely ribbed. 



M. mayi, Gatliff & Gabriel, 2 is also like it, but M. bractea 

 differs by lacking radial sculpture, by being more inflated and 

 closer ribbed. 



II ah. — Several specimens from too fathoms, forty miles 

 south of Cape Wiles, South Australia. 



CORBIS PERCOSTATA, Sp. UOV. 



(Plate xvii., figs. 9, 10, 11, 12.) 

 Shell small, rather solid, inflated inequilateral, anteriorly 

 produced, dorsal margin rather straight, ventral margin 

 rounded. I'mbo incurved, bearing a distinct prodissoconch. 

 Sculpture : About thirty-two elevated, strong concentric ribs 

 run from end to end and closely follow one another from the 

 umbo to the ventral margin. From each rib a thin broad 

 flange arching downwards conceals most of the interspace 

 between the ribs. Lunule small, limited by an indistinct 

 groove. Pallial line entire, running from one adductor to the 

 other. Within the ventral margin is set a line of small 

 sockets and tubercles about forty-five in number. Dentition : 

 In the right are two cardinals, the posterior strongest, the 

 anterior half the size of its fellow, compressed and parallel to 

 the hinge plate, anteriorly and posteriorly a slender lateral. 

 In the left, the anterior cardinal of typical Corhis is repre- 

 sented by a minute tubercle, posterior cardinal is strong and 

 pointed. Anteriorly a groove receives the right lateral, 

 posteriorly the margin of the valve is produced to act as a 

 lateral. Behind the main cardinals is a slight and elongate 

 chondrophore. Length 4'5, height 3*6, depth of single valve 

 I "3 mm. 



1 Sowerby— Proc. Zool. Soc, 1883, p. 31. pi. vii., f. 2, and Hedley— Mem. 



Austr". Mus.. iv., 1902, p. 319. 



2 Gatliff & Gabriel— Proc. Roy. Soc. Vict., xxiv., n.s., 1911, p. 189, pi. xlvii., 



flss. 8-12. 



