104 



Pecten consobrinus, spec. nov. Plate iii., fig. 6. 



Shell orbicular, fau-shaped, slightly convex, equilateral, 

 subinequivalve, the left valve somewhat flatter. Ornamented 

 with about eight radial folds and numerous (about 100) thickish 

 riblets ; the riblets are rigid, unequal in size, and separated 

 by irregular intervals which are minutely granular and usually 

 broader than the riblets. 



Right valve with rayed, unequal ears ; anterior ear larger, 

 subaliiform, slightly notched on the underside ; posterior ear 

 triangular, perpendicularly truncated. Ears of left valve 

 unequal, radially ribbed; the anterior one larger, triangular, 

 ■outer margin curved ; posterior ear triangular, perpendicularly 

 truncated. 



Dimensions. — Length and height about 85 millimetres. 



Localities. — Oyster banks of the Upper Aldinga series at 

 Aldinga and Hallett's Cove, St. Vincent Grulf. 



It is with some hesitation that I separate these shells from 

 P. hifrons, but the slight differential characters relied on are 

 observable at all stages of growth ; thus left yalves of 15 

 millimetres diameter are distinguished by their three-ridged 

 radial ribs ; at 30 millimetres diameter, whilst P. hifrons has yet 

 the elevated simple scaly ribs and plain furrows, P. consohri- 

 nus has almost lost the plicae which are replaced by four or five 

 threads, and about three occupy the furrows ; these diver- 

 gencies culminate in the very numerous radial threads and 

 obsolete folds of the adult. Similar changes are observable in 

 the other valve. P. consobrinus is moreover less iuequivalve 

 than P. hifrons. 



Pecten subbifrons. Tate. Plate iii., fig. 2. 



Pe/.—Proc. Eoy. Soc. S. Australia, vol. iv., p. 44. 1882. 



Shell orbicular or triangularly orbicular, fan-shaped, equi- 

 lateral, slightly inequivalve, umbos depressed. 



Eight valve slightly convex, rayed with twelve compressed 

 truncated ribs about equalling in width to the deep flatly con- 

 cave furrows ; the ribs carry two or three irregularly granular 

 nodose riblets, and there may be one or two raised lines in the 

 furrows. The surface, save on the riblets, granular-shagreen. 

 Ears rayed, unequal; the interior one much larger, outwardly 

 curved and sinuated below ; posterior triangular. Left valve 

 rather flatter than the right, but with similar ornament ; ears 

 isubequal, obtuse-angled, rayed. Interior of both valves plicated 

 but not ribbed. 



Dimensions. — Length and height, 50 millimetres ; a smaller 

 specimen, length 28, height 30 millimetres. 



Localities. — Oyster beds, Government house quarry, Adelaide 

 (M.T.)j Poiyzoal-bed, mouth of E. Onkaparinga. 



