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 striae. 



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, 2| mm. 



Remarks. I had classified this as L. Matthew sianus f 

 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. 



31. Plaxiphora zebra, sp. nov. 

 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 striae 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. 



