Older Tertiary of Victoria. 23 



Area capulopsis, sp. nov. (PI. II., Figs. 1, 2). 



Description. — Shell elongate, trapeziform, with a very straight 

 hinge, and a strikingly marked hinge area, umbo somewhat 

 conically elevated obliquely, and forwardly directed towards the 

 anterior end. The hinge area extends the full length of the hinge, 

 and occupies a relatively large space between the hinge and umbo, 

 is slightly concavely excavated towards the umbo, the latter being 

 a little elevated above the hinge line from the internal aspect, 

 the hinge area is smooth but for a number of lineations parallel 

 to the hinge, and is strongly angularly marked off from the 

 remainder of the shell. 



Posteriorly the shell is again angularly keeled from the umbo 

 to the extreme extension of the posterior margin, the space 

 between this keel and the angulation of the hinge being rather 

 strongly radially ridged, the number of strong ridges being 

 usually about five, and these are crossed by close lamellae 

 parallel to the lines of growth giving rise to frills. The 

 convexity of the umbo is indented medially, the indentation 

 broading somewhat towards the distinct sinus in the otherwise 

 slightly convex ventral margin. Anterior margin slightly 

 convex, posterior somewhat obliquely truncated to the hinge line. 



Surface ornamented with closely packed radial ridges, all of 

 which do not reach the umbonal region, the short ridges being 

 usually noticeable towards the anterior end, the ridges are 

 crossed by close lamellae parallel to the lines of growth, the 

 latter occasionally showing as more elevated and irregular ridges. 



Internally the anterior margin is a little crenulate. 



Dimensions. — Type specimen, antero-posterior diameter, 10 

 mm.; dorso-ventral diameter posterior to the umbo, 5 mm.; 

 anterior to the umbo, 3'5 mm. Larger specimens give antero- 

 posterior diameter, 15 mm.; and dorso-ventral, posterior 7 mm., 

 anterior, 5 "5 mm. 



Localities. — Eocene clays of G rice's Creek, Mornington ; Type, 

 Eocene clays of Orphanage Hill, Geelong (T. S. Hall) ; Eocene 

 sandy clays of Corio Bay, Geelong ; Miocene sandy clays of 

 Forsyth's section, Grange Burn, probably derived (T. S. Hall). 



