IREDALE : THE CHITONS OF THE KEKMADEC ISLANDS. 33 



has been recorded from the Chatham Islands, but it is doubtful 

 whether this identification be correct. Thiele has recently described 

 P. schaiimslandi from that locality, and this species does not belong to 

 the sub-genus Poneroplax^ but to the sub-genus Maorichiton. The 

 sub-genus Fremhleya, founded upon a New Zealand species, wrongly 

 ascribed to Australia, appears to have a representative on that 

 continent in my P. matthewsi. The sub-genus Maorichitonis typically 

 Neozelanic, but it seems to include the small Plaxiphora recently 

 described from South Africa and Ceylon. 



Thiele has given excellent figures of the fifth and posterior valves 

 of all these Plaxiphora, and I propose to give similar figures, 

 elucidating the above classification, in a paper now in preparation. 

 The species of Plaxiphora collected at tlie Kermadec Islands belongs 

 to the sub-genus Maorichiton. 



Pi.AXirnoRA (Maorichiton) mixta, n.sp. PL II, Figs. 12, 15, 16, 18. 



Shell small, elongate, somewhat elevated, valves keeled and beaked, 

 girdle densely hairy. Coloration generally black, white, and green. 

 Some specimens agree most accurately with E. A. Smith's description 

 of his C. terminalis as regards coloration ; sometimes dark blue with 

 white raurkings ; rarely rich brown with white markings; girdle 

 always green. Anterior valve with eight radiating ribs not much 

 elevated, and between eaah rib wrinkled V-sculpture. Median valves 

 with the lateral area bounded on both sides by strong raised, some- 

 what nodulous ribs, between which appears a transversely wrinkled or 

 V-sculpture; the pleural areas sculptured with irregular fine wavy 

 longitudinal ridges, more pronounced at the edges, and becoming very 

 fine on the dorsal area. Posterior valve triangular with the mucro 

 terminal, and the posterior area reduced to raised ribs; the anterior 

 portion sculptured like the pleural areas of the median valves. Inside 

 coloration deep blue-green. Anterior valve with projecting insertion- 

 plate, with grooved, widely spaced, somewhat irregular teeth ; the slits 

 eight in number. Median valves with projecting insertion-plate with 

 one slit ; sutural laminae widely placed apart and whitish in colour, 

 inside as well as out. Posterior valve with no insertion-plate, but 

 a callused semicircular ridge, which is much exceeded by the pointed 

 tegmentum. Girdle densely covered with long hairs, which are some- 

 what longer and bunched at the pores. Young specimens show the 

 sculpture to be much stronger in the juvenile, the pleural areas of 

 the median valves having well-marked and deep longitudinal ridges, 

 and the lateral areas are bounded by heavy, somewhat nodulous ribs. 

 The majority of adult specimens are covered with marine growths, 

 and the tegmentum is much eroded. Length of type 32, breadth 15mm. 



ITah. — Sunday Island, Kermadec Group (type) ; ? Macauley 

 Island, Kermadec Group. 



Station. — At Sunday Island it was rarely found in crevices of rocks 

 between tide marks. I collected a few specimens at Macauley Island 

 in deep rock pools between tides, but I am not satisfied that these are 

 identical with the one here described. 



VOL. XI. — MARCH, 1914. 3 



