280 



I have now received a reply from Mr. Tom Ire- 

 dale, dated July 7 last, in which he says, ''The form 

 saundersi appears to belong to cariosus, but I have not 

 definitely settled it." This rather confirms my surmise. 

 (See note Trans. Boy. Soc. S. Austr., vol. xliii., 1919, p. 73.) 



Juvenile Forms. 



It appears that very little has been done in the identi- 

 fication of the juvenile forms of the various species of Aus- 

 tralian chitons. In the course of my investigations I have found 

 that it is no unusual thing for the chiton in its juvenile stage 

 to differ so widely from the adult that it has been classed as a 

 different species. Thus the distinguishing features of the 

 adult are often entirely absent in the young, and the juveniles 

 of widely-separated forms have been confused together. 



I now add some notes on this subject, my conclusions being 

 founded on the examination of a very long series and from a 

 large number of different localities : — 



I. atkinsoni, Ire. and May, and II. sub-viridis, Ire. and 

 May. — Juveniles of these two rather widely-separated forms 

 are found living together in southern Tasmania, and are diffi- 

 cult to separate. The smooth dorsal area of the latter separates 

 it from atkinsoni, and the scales of atkinsoni are larger and 

 more strongly striated. 



I. atkinsoni lincolnensis , Ashby. — The juvenile form has 

 the whole of the dorsal area smooth ; all other areas are finely 

 decussate, and the shell, proportionately broader than the 

 adult form, is often rich buff, sometimes pure white. This was 

 the shell that was wrongly identified as /. pura, Sykes, in my 

 1918 Distribution List. This species always has striated scales, 

 v^hereas in /. 'pura they are smooth. 



Heterozona cariosus^ Pilsbry. — Juveniles of this specie® up 

 to a very considerable size — anyhow up to 12 mm. in length — 

 show none of the large pointed scales which are the dis- 

 tinguishing character of the genus. 



These juvenile shells have been classed as ''red or 

 orange," /. crispus, Reeve, by most collectors, and, latterly, 

 as Z. atkinsoni, Ire. and May, they having in common with 

 that species small, finely-striated scales. They can be separ- 

 ated from 7. lincolnensis, Ashby, by their lack of carination, 

 the shell being evenly arched, and also by the scales not being 

 bent over. In size and shape the scales are very similar. 



Some six months ago I examined the shell that is 

 recorded by Dr. Torr (Trans. Roy. Soc. S. Austr., vol. xxxvi., 



