103 



I have been indebted for the opportunity of exploring Wes- 

 tern Australian Polyplacophora. 



27. Plaxiphora hedleyi, sp. nov. 

 Plate xxiv., figs. 2a,b,c,d,e,f. 



General Appearance. Shell ovate, narrowing toward the 

 anterior, side slopes curved. Colour pale-green with five black 

 ;and white zebra stripes in the pleural area. The articula- 

 mentum is a milky- white with dark splashes at the sutures. 



Anterior Valve. Radially ribbed with eight rounded 

 icostse dying off toward the apex. These correspond with the 

 eight slit rays in the interior of this valve. 



Posterior Valve. Insertion plate smooth, unslit, like all 

 plaxiphora. Sinus broad and rounded. Insertion plates 

 large. Colour, milky-white, splashed with brown a-nd black 

 stripes. 



Median Valve. Dorsal area beaked, forming an equi- 

 lateral triangle, with a central ridge almost smooth and 

 splashed longitudinally on its posterior margin, with 

 black-and-white stripes varying in different valves. In 

 one valve microscopic striae run out diagonally from the 

 central area. To the unaided eye the dorsal area is pale-green, 

 smooth, and horny. The division between the dorsal and 

 pleural areas is distinctly marked by five white and five 

 black zebra bands, small toward the apex and lengthening 

 toward the girdle. The pleural and lateral areas seem to 

 run into one another, a slightly raised radial rib marking the 

 'division. The pleural and lateral areas have a mottled 

 .appearance, with splashes of brown and white or black and 

 white. The internal part is a milky- white with a distinctly- 

 raised rib, broad at the apex and narrowing off to one tiny 

 slit. The sinus is broad and the sutural plates neatly 

 icurved. 



Girdle. Leathery with microscopic granulations. Nar- 

 row with sutural horny protuberances, some spikes remaining. 

 Colour alternately black and white, black at the valves and 

 white at the sutures, 11 or 12 stripes of each colour on each 

 ^ide. 



Measurement. Dried specimen. Length, 16 mm.; 

 breadth, 11 mm. 



Habitat. Rabbit Island, Albany. Two live specimens 

 .and one median valve. 



Remarks. This specimen has been named after Mr. 

 Hedley, conchologist, whose wide conchological information 

 thas helped many a beginner. The zebra-like stripes will 

 cause this specimen to be easily distinguished. 



