100 rUOCEEDINGS OF THE MALACOLOGICAL SOCIETr. 



We find the sculpture of the valves in P. hiraniosa, P. ccelata, 

 P. ovtda, and P. petholata to be almost identical. 



JIab. —Yvom. Auckland to the Blutf, but nowhere common. 



10. Plaxipeoe.v SuTKKr, Pilsbry. 



PJaiciphora Suteri, Pilsbry: Nautilus, vol. viii (1894), p. 8. 

 Mopalia ciliata, Soworby : Huttou, Man. ]S"ew Zealand AIoll., p. 116 

 {non Sowerby). 



This handsome Chiton is in size and form not unlike P. glaucn, 

 Quoy & Gaim., and is only found in exposed situations on rocks, the 

 valves mostly covered with calcareous growth. Young specimens are 

 sometimes found on 3[ytilns lafus. 



llah. — From Manukan Harbour to Foveaux Strait ; rather rare. 



11. Plaxiphora. subatkata (Pilsbry). 



Tonicia atrata, Sowerby : Hutton, Man. New Zealand Moll., p. 114 



{7ion Sowerby). 

 Tonicia stibatrata, Pilsbry: Man. Conch., ser. I, vol. xiv (1893), p. 201. 



Shell large, oval, moderately elevated ; side slopes slightly arched ; 

 ridge rounded. Colour reddish -brown, dirty pink at the jugum. The 

 head valve strongly concentrically ridged, and with eight radiate ribs, 

 which, however, sometimes become obsolete. Central valves beaked 

 anteriorly and posteriorly ; the anterior beak is rather prominent, 

 rounded, the posterior one pointed, forming an angle of about 120°, 

 and is formed by the outer layer only. The wliole surface of the 

 median valves is strongly concentrically striated, following the outline 

 of the anterior beak over the jugum. Lateral areas distinct, raised, 

 with two ribs, which are sometimes flatly nodulous, owing to their 

 being crossed by concentric lines ; in some specimens the diagonal ribs 

 are only very faint, or disappear altogether ; on the other hand, their 

 number may increase to four, but the anterior and slit-rib are always 

 the more prominent. Posterior valve small, depressed, concentrically 

 ridged, .slightly beaked anteriorly ; mucro inconspicuous, terminal. 

 Interior white, tinged with light-blue. Sinus shallow, rounded. 

 Sutural lamina) rather broadly rounded. Insertion plates low. Anterior 

 valve with eight iiTcgularly distributed slits ; teeth sharp, striated on 

 tlie outer side; the whole of the interior light- blue. Intermediate 

 valves with one slit on each side ; posterior tooth broad ; a strong 

 light-blue callosity extends between the two anterior teeth. Posterior 

 valve with the insertion plate thick, rounded, without slits, a small 

 sinus in the middle behind. In all valves the eaves are very narrow 

 and spongy. Girdle wide, narrower at both ends, leathery, tan-colour, 

 dark brown when dry ; at each suture a pore with long corneous 

 bristles, six in a tuft, and alternating with these pores a second row 

 of smaller ones is situated near the margin. In front of head and 

 tail valve six smaller pores with short bristles. The margin beset 

 with horny bristles of varying size. Length 75, breadth 45 mm. ; 

 divergence 125° (sjnrit specimen). 



