SUTKR : REVISION OF THE NEW ZEALAND POLYPLACOPHORA. 69 



jjah. — Cook Straits, Foveaux Straits, in the latter locality in about 

 15 fath. 



Type in the Colonial Museum, \N'ellington. 



At the end of 1898 Dr. Pilsbry veiy kindly brought the fact under my 

 notice that my A. costatus was not the same as the Australian shell, and 

 that it had to be called A. ruhiginoms, Hutton. Being unable to procure a 

 specimen of A. rostafii,^, Mr. Etheridge, jun., Curator of the Australian 

 Museum, Sydney, informing me that only two specimens had ever been 

 found, and that it was unknown to Australian collectors, I now proceed to 

 point out the difference of the two species from Smith's diagnosis in Man. 

 Conch. — : A. cosfafus is more elongated and narrower than A. riihiginostLs, 

 the respective ratios being i : 2, 6 and i : i, 3. A. costaius has the lateral 

 areas well defined by a raised keel, which is absent in ruhiginoms. The 

 posterior valve of costaius has six radiating ridges and the insertion plate 

 with 6 notches, against no ridges and and 4 slits in ruhiginos^a. The colour 

 of ro^fatux is pale brown, whilst ruJiiginoms is sometimes beautifully 

 coloured, producing quite a kaleidoscopic aspect, as Dr. Torr correctly ex- 

 pressed himself when I lately showed him some specimens in my collection. 

 Chiton quoyi, Desh., n. suh-sp. limosa. 

 Cluton (freii.^, Suter : Proc. Malac. Soc. Lond., 1897, vol. ii, p. 195, 



non Reeve. 

 ^^'hen I wrote the Revision of the New Zealand Polyplacophora in 1897 

 I had not seen the true C. aereus, Reeve, which seems to be a very rare 

 species. I sent a specimen of my supposed aereus to Dr. Pilsbry in 1898, 

 and he told me that it was only a slight form of 0. quoyi^ not specifically 

 distinct, and not the true aer>'ii!<. I also sent specimens to Mr. E. R. Sykes, 

 of Ix)ndon, askjng him to kindly coaipare it with the type specimen in the 

 Pritish Museum. With his usual obliging readiness he sent me the following 

 information : " If the specimen, presumably type, in the Prit. Mus. can be 

 trustrd, )()ur Chitons are not, T think, aerrux : the sculi)ture on tliat species 

 is miirli .stronger and coarser on the median areas, i.e. more like that ot 

 canal irulalux. 'I lie Museum ai'irux is larger — nearly twice the size — and of 

 an olivaceous green." A few years later I received some specimens of a 

 Chiton from Mr. Murdoch, Wanganui, which he had found near Cape 

 Egmont, antl these proved to be the true ('. arrcuK, Rei.-ve. It is indeed 

 very different from my supposed aereus, \vhi<h I now class as a sub-species 

 of C. guoyi^ Desh. It differs from the species in being smaller and narrower, 

 the jugum angled, not carinated, not always smooth, colour yellowish to 

 green, mostly coated with blackish-green. Anterior valve with 8, posterior 

 vahi' with 15 slits, divergence about 100'', against 120' in the species. 

 Length 20, breadth 12 millim. 



Il(tl). — Under stones on mud ll;its in Manukan and Auckland Har- 

 bours. 



Type in my^col lection. 



