Section ibiadara Sraj;. 

 ARGA (MADARA) DASEIA ,,. 30. 



Description .- '^hell of ms^iurasize, heavy, suTDrhornlDOiflal, 

 elongate, much inflated, slip:htly hig-her in the posterior region, 

 the anterior marsrin ctTrving broadly imto the gently arched ventral 

 mar^'in; obliquely truncater! posteriorly; ixrabones high, decicle;ily 

 inflate'!, the tip slightly Impressed medially, situated at about 

 the anterior third of the length; left valve sculptured with 

 twenty-six hiR-h, square radial ribs, separated by v/ider deeply chan- 

 nellel interspaces; on the posterior slope the ribs lower and flat- 

 ter, the anterior ribs about as wide as the interspaces; concentric 

 sculpture of increment als, elevated at integrals, producing faint 

 nodulations on the tops of the ribs and inconspicuous raisei lines 

 on the sides of the ribs and in the Inters-oaces ; cardinal area 

 impressec!, of moderate width, wider in front of the umbo, with five 

 ligament grooves behind the umbo and five longitudinal striations 

 before; hinge long, straight, v;ith fine numerous teeth, larger and 

 slightly oblique distally; inner margin of the valve v;ith short, 

 broad, deep crenulations. 



Pi tensions .- length, 31.5 mm.; alt., 19 mm.; seraidiam., 

 1'" mm. ; length of hirjge, 25 mm. 



