61 



the growth lines; also in some of the valves the ribbing shows 

 a subpustulose tendency ; the posterior margin is finely- 

 serrated. Pleural area and dorsal area covered with closely- 

 packed wavy longitudinal ribbing, which is decussated or 

 bridged in the dorsal area and partly in the pleural area; 

 eaves prominent; insertion plates fluted on upper side and 

 very strongly toothed with sharp saw-like teeth ; sutural 

 laminae much produced; sinus broad and lobed. 



Girdle. — In dried specimen 8 mm. wide in front, or 

 without the flattened appendages, 5 mm. in front and half 

 that width behind, cleft for half its width at tail, very closely 

 beset with solid, irregular, minute scales. But the most 

 marked feature is a large number of coarse, branching, brown 

 hairs or spicules up to 4 mm. in length, placed in an irregular 

 double row, spaced from 2 to 3 mm. apart in the anterior half, 

 but hardly present in the posterior half. Each branch of 

 these hairs has an ovate, spindle-shaped terminal, reminding 

 one of a white stiletto, but they are too broad to be described 

 by that term, and may be better described as sharply-pointed 

 white cylinders or spear-heads, which are at their base twice the 

 thickness of the hair to which they are attached. These strange 

 white spicules are clustered thickly at the base of and along the 

 centres of the flattened finger-like processes, before referred 

 to; these are sessile, rising straight out of the girdle. There 

 seems to be some relation between these spicules and the 

 protruding portions of the girdle, as they and the hairs to 

 which they are attached are only present opposite these. There 

 are a few scattered about the girdle not in the main double row. 



Measurements. — The specimen described in the foregoing 

 is 67 x 41 mm. Another, taken at the same time, now in Mr. 

 May's collection, measures 68 x 47 mm. ; and one I found 

 washed up on the beach at Aldinga Bay is 68 x 48 mm. When 

 alive the girdle would add somewhat to the foregoing 

 measurements. 



Habitat. — I first took this shell alive at Marino in 1897, 

 in a deep hole at lowest tide, and I believe no other was found 

 at) this locality until March 7, 1917, just twenty years later, 

 when I found the two of which measurements are given above, 

 both in the same hole, adhering to the upper side of a rock at 

 lowest spring tide. All three were so densely covered with 

 growth that they were most difficult to detect. I have twice 

 found specimens washed ashore at Aldinga. Bay, and Adams 

 and Angas' type came from Rapid Bay, a little further down 

 the gulf. Dr. Verco dredged a few specimens in the same 

 gulf, so we may conclude that it is a fairly deep-water species. 



Comparisons with other specimens. — I have one that I 

 found washed up at Aldinga Bay, measuring 35 x 28 mm. dry, 



