18 



AcANTHOCHiTON coxi, Pilsbry. 



(Naut., vii., p. 119, Feb., 1894; Proc. Aoad. Nat. Sci. Pbil., 

 1894, p. 80, pi. iii., figs. 21-26, pi. iv., fig. 34; A. lachrymosa, May 

 aiiid Torr, P. and Proc. Roy. Soc. Tas., 1912, pp. 36 and 37, pi. i., 

 figs. 1-4.) 



Tlie identification of this Acanthochiton lias always been 

 a difficulty with me. In July, 1919, I wrote the Australian 

 Mu&eum for the loan of a specimen, and at their suggestion 

 Mr. Bassett Hull very kindly sent me a shell which, on exam- 

 ination, I found could not possibly be A. coxi; but, strangely 

 enough, it was a worn specimen of a species described by 

 Dr. Torr and the writer in October, 1898, under the name 

 of A. crocodilus, and which, up till the identification of Mr. 

 Hull's specimen from New South Wales, was only known to 

 occur in South Australia, and limited to the pair originally 

 described, which were side by side on the same rock, at low 

 water, at Marino. 



Later on I received specimens from Dr. Torr's collection 

 and the Queensland Museum, labelled A. coxi, but in both 

 cases they were misidentifications and referable to well-known 

 species. Through some oversight, although I again applied 

 to the Australian Museum for the loan of their co-type, it 

 was never sent for my inspection. 



In correspondence with Professor Dr. J. Thiele, of Berlin, 

 I mentioned my desire to see coxi, and he was good enough 

 to send me a specimen from Balmoral, which I conclude is the 

 place of that name in North Borneo. The specimen was 

 marked ''identification uncertain." If it had come from Tas- 

 mania one would have no hesitation in identifying it as a 

 slight variant of A. lachrymosa, May and Torr. 



It differs from the Tasmanian shells, slightly, in the 

 arrangement of the pustules, and the spicules on the girdle 

 are slightly coarser. On writing Mr. W. L. May he advised 

 me that he had some years ago seen the co-type of coxi in the 

 Australian Museum and had made a note that it was very 

 close to lachrymosa. In October last, Mr. May brought over 

 a very fine series of lachrymosa from the type locality. We 

 found that the sculpture varied from long, slender, flat, finger- 

 like processes to short oval discs, or elongated tear-drop 

 pustules. Most in the juvenile stage have quite small pus- 

 tules, but even in this they are not consistent. They also 

 vary very much in the spacing of the pustules ; mostly they are 

 crowded, as is so well shown in the figures accompanying May 

 and Torr's description. I.e. 



A comparison of these figures with the figures in Dr. 

 Pilsbry's paper on "Port Jackson Chitons," I.e., will explain 

 the difficulty we have all laboured under in identifying A. 



