168 



Anterior Valve. — Three sharply-defined riblets. Covered 

 with rounded or oblong pustules larger at the margin and 

 decreasing in size towards .the apex. Interior pearly. Inser- 

 tion plates deep, three slits. 



Median Valve. — Dorsal area, wedge-shaped, foliated, 

 covered with microscopic triangular pustules. Alternate 

 black and white spots separate the dorsal from the pleural 

 areas. Latero-pleural area, covered with irregular rounded 

 and elliptical tubercles, small near the dorsal area, growing 

 much larger as they approach the girdle and the posterior 

 edge. Sinus broad, insertion plates deep, one slit on each 

 side. 



Posterior Valve. — Diminutive, mucro median, a distinct 

 dorsal area similar to the median valves with irregular pus- 

 tules below the mucro. Five microscopic riblets run from 

 the mucro to the eaves. The dorsal area is concave. Articu- 

 lamentum, bluish-green, rounded, excavated, deep insertion 

 plates, two slits. 



Girdle. — Leathery, covered with spinelets. Five erect 

 silvery tufts stand out prominently around the anterior valve 

 and one tuft at each suture. The hollows in which these 

 tufts are placed is surrounded by a prominent ridge. 



Hah. — Aldinga (by Mr. Kimber, after whom the shell is 

 named), Kangaroo Island. 



Measurement. — Dried specimen, 10 x 4 mm. 



Remarks. — I have four specimens, varying somewhat 

 in appearance, but similar in detail. 



60. Ischnochiton levis, sp. nor. PL vi., figs. 6a-f. 



General Appearance. — Smooth, rounded, decidedly car- 

 inate, ffale-cream colour with spots of yellow, very broad in 

 proportion to length, valves narrow. 



Anterior Valve. — Smooth, except for a series of concen- 

 tric growth-lines, microscopically granulated. 



Median Valve. — Regular growth-lines appear over the 

 dorsal, lateral, and pleural areas. The lateral areas are 

 slightly raised, the growth-lines making four very large fine 

 longitudinal riblets. The pleural area is minutely reticulated. 



Posterior Valve. — Mucro ante-central. Two distinct 

 areas, dorsal and pleural, consisting of microscopic regular 

 granulations. The rest of the valve is smooth, almost flat, 

 with two or three concentric lines. Eight or nine irregutar 

 slits. 



Girdle. — Covered with rounded scales, microscopically 

 striated. 



Measurement. — 12 x 6 mm. 



