115 



Ca both, the right valve is moderately convex, and broadest 

 at about the dorsal two-fifths. In the following the con- 

 vexity is much greater, and the greatest width is medial. 



P. fumatus has the ribs roundly convex, but slightly 

 elevated, the furrows a little narrower than the ribs ; the 

 whole surface concentrically striated under the lens, not 

 raised into lamellae ; the ribs are radiately distantly striated; 

 external colour reddish-brown, internally white with a brown 

 border all round. P. fcmatus, tab albits differs in being 

 less convex, and in colouration ; the convex valve is white 

 inside and out, the flat valve exteriorly pinkish-white, the 

 ribs of a deeper tint, and streaked or blotched with darker 

 colour. 



P. bifidus, Menke, Moll. Nov. Holl., p. 35, 1843 (non 

 Minister in Goldfuss Petref. Germ.) is probably conspecific. 



Pecten mebidionalis. (Spec, nov.) 

 (P. meridionalis.) Brazier MS.) 



Eight or convex valve with about 16 radiating ribs ; whole 

 surface closely concentrically lamellose, more conspicuously 

 so in the furrows ; ribs convexly depressed, longitudinally 

 sulcated ; furrows concave, as wide or a little wider than the 

 ribs. Exterior colour purplish-grey, pale straw about the 

 umbo ; interior colour maroon around a white central 

 patch. 



Left or flat valve closely concentrically lamellose, ribs 

 roundly convex, furrows concave about as wide as the ribs, 

 exterior colour purplish-grey, interior maroon. 



Young shells up to 60 mills, long have the convex valve 

 both inside and out, white with a pinkish tinge towards the 

 margin ; the flat valve is ruddy-brown exteriorly, white with 

 ruddy-brown ribs interiorly. 



Dimensions of right valve of a large specimen :— -Antero- 

 posterior diameter, 120 ; ventro-dorsal diameter, 104 ; 

 ventro-dorsal curve, 125 ; greatest depth at 40 from umbo, 

 27 millimetres. 



Localities. — Living on the shores of Tasmania. Possil in 

 the newer tertiary deposits at Ascot Heath, Eiver Glenelg, 

 Victoria. (J. Dennant!) 



Remarks on Distribution. 

 Pecten fumatus is restricted to New South Wales, whilst 

 P. alius is only known from St. Vincent-Gulf and Port 

 Lincoln in South Australia. The characters which separate 

 these forms may not be accepted by conchologists as of 

 specific value, and for the present I am content to regard the 

 latter as a variety or local race of the former. So far as 

 known, a thousand miles of coast line intervene between 



