231 



Cryptoplax michaelseni, Thiele, 1911. 



Mr. Johnston is to be heartily congratulated on the rediscovery of this 

 interesting little Cryptoplax. Until now no Australian worker has had an 

 opportunity of examining this species, our knowledge of it having been limited 

 to the single, minute example in the Berlin Museum. So outwardly is it like 

 members of the genus Acanthochiton that Dr. Thiele had disarticulated it before 

 he discovered that it belonged to quite a different group. A full description will 

 be given in another paper. 



Acanthochiton bednalli, Pilsbry, var. johnstoni, n. var. 

 (Pilsbry, Proc. Acad. Nat. Sci. Phil., 1894, p. 81, pi. ii., figs. 7-11.) 

 Three specimens, of which the largest measures 12X6^ mm., of a very pretty 

 Acanthochiton were collected at Carnarvon. In general appearance it differs 

 from A. bednalli, as we know it in South Australia and Tasmania. The differ- 

 ences I have been able to detect do not seem to warrant the giving to it full 

 specific rank, so I content myself, for the present, in distinguishing it under a 

 varietal name only, and have pleasure in naming it after the finder, Mr. Johnston. 

 I sent the three specimens to my friend, Mr. W. L. May, of Tasmania, and he 

 fully concurs with me in thinking that, at least, the shell deserves this distinction. 



Description. 



The ground colour is white, almost porcelain-white, with a regular zigzag 

 pattern and mottling of greenish-black. The girdle is dark, densely clothed with 

 white spicules, the hair tufts are white, and the girdle fringe is white. 



The dorsal area on valve 2, of two of the specimens, is bright pink, and on 

 the other rufous. The sculpture seems normal except that the dorsal area is 

 decidedly narrower than in typical A. bednalli, and has none of the deep, longi- 

 tudinal grooving so characteristic of that species. A large portion of that area 

 is quite smooth and polished, but possesses subcutaneous, longitudinal lining, in 

 this respect corresponding with A. granostriatus. There can be detected on 

 several of the dorsal areas, especially at the sides next the pleural area, some 

 broken, longitudinal scratching. It is just possible, though perhaps improbable, 

 that this feature, together with the longitudinal, subcutaneous lining, are survivals 

 of the deep, longitudinal grooving of typical A. bednalli. 



Dr. Thiele recorded A. bednalli as having been collected at Shark Bay by 

 Drs. Michaelsen and Hartmeyer. I conclude, therefore, that it was the present 

 form that they took; nevertheless I cannot but think, after all, this may prove 

 a distinct species. The thoroughly tropical character of the fauna leads one to 

 suspect that the characters of this shell rather simulate those of A. bednalli, 

 than that there is any near relation. 



ScLERocHiTON MILES, (Carpenter) Pilsbry, 1892. 



PI. xviii., figs. 3, a, b, c, d. 



(Chiton miles. Carp. MS.; Sclcrochiton miles, (Carp.) Pilsbry, Man. Con., xiv., p. 189, 

 pi. 46, figs./ 1-5, 1892; Sclerochiton ciirtisianus, Smith of Ashby, Jour, and Proc. Roy. Soc. 

 W. Austr., vol. vii., 1921-2, p. 34; non Chiton miles, Pils. of Hedley, Marine Fauna Q'land, 

 1909; non Sclerochiton miles, (Carp.) of Thiele, Rev. des Sys. der Chitonen, pt. ii., p. 94.) 



Amongst the chitons from Carnarvon are several with large, imbricating, 

 girdle scales, simulating in general appearance Sypharochiton pellis-serpentis, 

 which in sculpture and in the possession of eyes still more closely simulating pale 

 forms of Liolophnra hirtosus. In addition, the absolute absence of radial rib- 

 bing further separates it from these. On comparison with specimens in mv 



