65 



bonal ridge extending to the somewhat pointed post- ventral 

 extremity ; post-dorsal margin gently sloping for half its 

 length, thence more abruptly descending to form an acute angle 

 with the moderately convex ventral margin. 



The right valve has the anterior lateral tooth thick and 

 short, the posterior longer and less stout; the doubling of these 

 laterals is but faintly exhibited ; the cardinal tooth is small. 

 In the left valve there are no traces of the superior and supple- 

 mentary laterals. 



Pallial line with a broad, very shallow, posterior emargination 



Dimensions. — Antero-posterior diameter, 125 ; umbo-veubral. 

 diameter, 9'5 ; sectional diameter, 6 millimetres. 



Locality. — Living in great abundance on the sandy bottom 

 of Lake MacDonnell, Great Australian Bight. Lake MacDon- 

 nell is now entirely cut off from the ocean by lofty sanddunes ; 

 Zosterap and other plants, as also several species of mollusca, 

 still inhabit it. 



The nearest ally of this pretty species is 31. cuneata, Chem. 

 It also bears some general resemblance to Spisula Jluviatilis,. 

 Angas, but is more oblique and gibbous, not sharply angulated 

 at the post-umbonal slope, and the dentition is very different. 



Psammobia Brazieri, spec. nov. Plate v., fig. 1. 



Shell elongate, somewhat donaciform, thin, shining, pellucid, 

 slightly gaping at both ends, depressed : umbos small, acute, 

 directed posteriorly, and situated far back. 



The front dorsal margin is almost three times as long as the 

 posterior, nearly horizontal and straight; the post-dorsal slope 

 is very oblique and straightish. The ventral outline is but 

 slightly curved, forming an obtuse rounded extremity an- 

 teriorly, and a blunt angle with the obliquely truncated pos- 

 terior extremity. The posterior area is bounded by an acute 

 umbonal carina, a little anterior to which on the interior is a 

 thick ridge descending from the umbo and appearing on the 

 exterior as an opaque white line. 



Colour whitish, with a pink flame enclosed between the 

 carina and the internal umbonal ridge. The sculpture consists 

 of fine concentric lines of growth, becoming coarser on the 

 posterior slope. 



Dimensions. — Antero-posterior diameter, 12 ; length of pos- 

 terior side, 3*5 ; umbonal ventral diameter, 6 5 ; sectional 

 diameter of united valves, 2*25 millimetres. 



Locality. — Aldinga Bay. 



Tellina subdiluta, spec. nov. Plate iv., fig. 9. 

 Shell small, thin, semipellucid, white or pale yellow, shining ; 

 ornamented with close, regular, flat concentric ridges and linear 

 interspaces ; the ridges are slightly elevated, lamellar, fewer 



