82 PROCEEDINGS OF THE ACADEMY OF [1894. 



straight. Color of valves light creamy-gray, sparsely maculated 

 with dingy browu and white, usually sliowing some indistinct olive 

 stains on some valves. Girdle gray, witli conspicuous silky, silvery 

 tufts. 



The posterior (sutural ) margins of the valves are nearly straight, 

 the small beaks slightly projecting along the middle line. The teg- 

 mentum of each intermediate valve is divided into a distinct but not 

 sharply defined triangular dorsal area, which is longitudinally 

 marked by ir)-20 (heply cut ><ti-kz, and twosubequilateral triangular 

 side areas, wliic^h bear concave or flat t()})ped ovate pustules, rather 

 irregularly arranged. The anterior valve is similarly sculptured; 

 and has several indistinct radial elevations; the front slope of its teg- 

 mentum is nearly double the length of the anterior teeth. The pos- 

 terior valve has a rounded-hexagonal tegmentum which is somewhat 

 broader than long, with the raucro between the posterior third and 

 fourth of its length; behind the miicro sloping outward. 



Interior tinged with rose in the middle and somewhat porous there, 

 the teeth and sutural plates bluish or greenish; valve-callus strong; 

 reflexed border of tegmentum very narrow. Anterior valve with 

 five, intermediate valves 1-1 slits; posterior valve (PI. II, figs. 

 (S-10) having a distinctly biangular, bilobed contour behind; the pos- 

 terior median portion straight, iatero- posterior sides concave behind 

 the two narrow slits. Sinus wide and angular in all the valves. 



Girdle wide, densely clothed with short, gray- brown si)icules, and 

 having nine large tufts of long, silvery sjjicules on each side. 



Length about 13, breadth 6'' mm. (dried specimen). 



Habitat : Western Shore of St. Vincent Gulf, S. Australia (W. 

 T. Bednallj. 



This species is closely allied to A. (jranostriatus, but the valves 

 are more solid; the dorsal areas are in iicji more deephj striated long i- 

 tiidiiKiUij ; that of valve viii is largely broken into granules. The 

 sutural lamime in A. hednalli are greenish; the pustules of the side- 

 areas are somewhat larger and rather less regularly arranged in 

 longitudinal series. The profile of valve viii is not notably different 

 in the two species, but the mucro of A. gr(iuostri((tiis is rather more 

 posterior. A. Bednafl! differs from A. Co.ri in having much more 

 conspicuous and silky sutural tufts, in the color of the interior and 

 sutural lamina', in the flat pustules, and in lacking the curved dia- 



