402 



needed to justify the placing of the four very distinct forms 

 herein dealt with under the specific name of G. antiquus, 

 Reeve, as subspecies thereof. I take it that true science is 

 better served in showing their affinities, rather than magnify- 

 ing their differences. We may conclude that all four species 

 have a common ancestry, but that each of the widely separated 

 localities has developed a fixed type of its own. 



In conclusion. — In my list of Australian Polyplacophora 

 (Trans. Roy. Soc. S. Austr., vol. xlii., 1918) under the heading 

 C alii sto chit on, two species and one subspecies were given, viz., 

 C. antiquus, Rve., 1847; C. recons, Thiele, 1911; and C. 

 mawlei, Ire. and May, 1916, the lastnamed being recorded as 

 from both South Australia and Victoria. As regards the first 

 it certainly was incorrect, and as far as I am aware it has not 

 yet been found in Victoria. 



Two more must be added to the list now, bringing the 

 total to five, and it is very probable that the very beautiful 

 shell described by Dr. Torr as Ischnochiton bednalli, may have 

 ultimately to be referred to this genus ; I have not yet seen a 

 disarticulated specimen, so cannot express a definite opinion. 

 Undoubtedly the network sculpture is suggestive of this 

 genus, but in some other respects it does not show any very 

 close affinity with any of our known Australian forms. 



Since finally typing the foregoing paper I have turned 

 up Iredale and May's description of C. may 'lei (Proc. Roy. 

 Soc, vol. xii., pts. ii. and iii., Nov. 1916) and cannot refrain 

 from quoting their concluding remarks on the differences : "in 

 the formation of the sutural laminae, these are continuous, 

 whereas they are widely separated in the species C . antiquus, 

 Reeve, and even more so in the South Australian species." 



Mr. S. Stillman Berry, of California, writes me on July 1, 

 1919: — 'Your alcoholic specimens of Gallistochiton (from 

 South Australia) do not look like the dry antiquus from 

 Sydney." I think it probable that when the Victorian fauna 

 is fully investigated we shall recognize two distinct species, 

 C. antiquus, extending from Queensland down the East Coast, 

 finding its extreme southern limit in Port Arthur, in Tas- 

 mania, where the subspecies 0. mawlei, I. and M., is its 

 representative, and a western species, extending from the sub- 

 merged Bassian Isthmus through South Australia and Western 

 Tasmania to Western Australia, of which the dominant form 

 will be C. meridionalis, herein described, with C. mayi, also 

 described herein, as its subspecies. 



Addenda. — After completing the draft of the foregoing 

 paper I received from Mr. C. J. Gabriel, of Melbourne, an 

 Acanthochiton which he had compared and identified with 

 Sykes' type of A. pilsbryi in the Melbourne Museum. Mr. 



