IKEDALi: : THK CHITONS OF THE KEKMADEC ISLANDS. 31 



and it was then found that the majority of these differed in their 

 depressed form and darker coloration, which was noticeable at sight. 

 Moreover, they were beantifully clean specimens such as had never 

 been collected before. In jS^ew Zealand eveu the smallest specimens 

 of these Chitons are covered with ugly extraneous growths, and the 

 earlier collected Kermadec specimens were dirty and worn. I have 

 now concluded that this depressed form must be a deeper water 

 dweller. It is easily separated from E. perplexus by its depressed 

 form, different posterior valve, and longer teeth, whilst the coloration 

 is also darker. It cannot be confused with either E. iiohilis (Gray) 

 or E. huttoni, Pilsbry, and, on account of its pseudo-resemblance to 

 the latter, I have called it E. imitator. 



There would seem to be grounds for supposing the depressed form 

 to be the oldest, as juveniles of all four species are very flattened 

 and scarcely determinable The girdle is simply leathery with 

 a crinkled appearance, with only signs of the short spiuelets thereon. 

 I have juveniles of the Kermadec species whicli I would not definitely 

 distinguish, since I do not think they could be easily differentiated 

 from juveniles of E. nobilis (Gray), which I collected in the South 

 Island of New Zealand. It is certain that the Kermadec species are 

 smaller than the New Zealand ones, the valves being comparatively 

 broader and the girdle comparatively narrower. The largest 

 Kermadec specimen is under 70 mm. long and 45 mm. broad, whilst 

 an average-sized NeozelaTiic E. nobilis, Gray, measures 75 mm. long 

 by 50 mm. broad, and specimens 110 mm. in length are known to 

 exist. These measurements are taken from specimens with the girdle 

 well preserved and flattened. 



family MOPALIID^. 

 Genus Plaxiphora. 

 Plaxiphora, Gray, Proc. Zool. Soc. LomL, 1847, pp. 65, 68, lt9. 



Type (by monotypy), Chiton carniichaelis, Gray = Ch. auratus, 

 Spalowsky. 



In the jlfanual of Concholngy, vol. xiv, p. 311, Pilsbry divided the 

 genus Plaxiphora into two sub-genera, Plaxiphora aiul Placophoropsis. 

 1 would separate these generically. Pilsbry then indicated three 

 sections, of his sub-genus Plaxiphora, viz. Plaxiphora (s.str.), 

 Guildingia, and Frembleya. Thiele (Revision, p. 116) admits two 

 genera, Plaxiphora and Frembleya, noting no sections. 



Gxiildingia 1 would generically differentiate, as the solitary species 

 is well defined and cannot be confused with anything else ; the valves 

 are distinctive, whilst the radula seems to differ. The type of 

 Plaxiphora is Chiton auratus, Spalowsky, and this species is well 

 characterized by its large size, the lack of sculpture, the nature of 

 the girdle, and the form of the posterior valve. The Neozelanic 

 Plaxiphora campbelli, Filliol, with which P. ancklandica, Suter 

 (Subant. Islands New Zeal., vol. i, Mollusca, p. 2, pi. i, fig. 1, 1909), 

 based upon a juvenile, is synonymous, is typical. 



