106 
slatish-grey on anterior and 5 median valves, posterior valve 
almost black. 
Anterior Valve. Longitudinally parallel rows of pus- 
tules. 
Posterior Valve. Almost black; umbo postmedian, with 
concentric pustulose striz. 
Median Valves. Regularly longitudinally granulosely 
striated. No difference in the dorsal, lateral, and pleural 
areas. 
Girdle. Diminutive, dark, scaly, and with spicules. 
Habitat. Under stones in shallow pools at Hopetoun, 
Western Australia. Only one specimen was found. 
Measurement. Dried specimen. Length, 4 mm.; 
breadth, 24 mm. ‘ 
Remarks. I had classified this as 1. Matthewsianus, 
Bednall, which is so common in South Australian waters, 
but on comparing them I found it much broader in propor- 
tion to its length, and the body of the animal which is 
uniformly red in L. Matthewsianus is almost black in L. 
Niger. I then placed it with L. Badius, Hedley and Hull, 
and found it very similar, with the exception that the grain 
rows were distinctly regular. Its dark appearance has given 
its name. 
81. PLAXIPHORA ZEBRA, Sp. 70U. 
5 FbuUC 
Plate xxv., fig. 6. 
A beautiful median valve was collected at Port Esper- 
ance and is worthy of a name. The valve is rounded. The 
dorsal area is indistinct with 10 irregular creamy tear-drop 
pustules in the centre forming a V with diagonal striations 
terminating in the anterior part of the valve. The lateral part 
of. the dorsal area has three or four transverse striz continued 
into the pleural area. The colour is a delicate pink, mottled 
with white and brown splashes. The pleural area has a num- 
ber of zigzag pustulose riblets running into the striations. 
coming from the dorsal area and narrowing toward the apex. 
Colour: Five alternate splashes of bright-red and creamy-white 
give the shell its name. The lateral area is distinctly raised 
with two rows of 9 or 10 large pustules on its anterior and pos- 
terior margins with a sulcus between, irregularly pustolose 
and striated. The pustules have the tear-drop appearance of 
those in the dorsal area. Interior is porcelainous, sinus 
curved, broad, shallow, and pectinated. The sutural plates. 
are small, one slit. The anterior part of the valve is folded 
over and an irregular sulcus is formed, terminating in the 
slit. ‘The specimen may have been bleached, so that the pink 
splashes in the pleural area may have been brown or black. 
