224 



A REVIEW OF ISCHNOCHITON (HAPLOPLAX) SMARAGDINUS, ANGAS, 



1867, AND ITS CONGENERS, TOGETHER WITH THE DESCRIPTION OF 



TWO NEW CHITONS FROM PAPUA. 



By Edwin Ashby. F.L.S., M.B.O.U. 



[Read June 14, 1923.] 



Plates XVI. to XIX. 



Before dealing with the Haploplax from Papua, for which, as well as other 

 forms dealt with later in this paper, my thanks are due to my friend Dr. W. G. 

 Torr, it became imperative to settle the question as to whether the shell described 

 by Bednall and Matthews, under the name Ischnochifon resplendens (Proc. Mai. 

 Soc, vol. vii., pt. 2, June, 1906), is distinct from the Sydney shell, which Avas 

 described by Angas under the name Lophyrus smaragidinus (Proc. Zoolog. Soc, 

 1867, p. 115, t. 13, f. 28; I.e., p. 222). Torr, in his paper on Western Australian 

 Chitons, in 1911, treated it as a distinct species, but in his paper of the next year, 

 considered it a colour variety of /. smarogdinus. Up to the present time no 

 one has published the results of any careful examination. A reference to Bednall 

 and Matthev/s' paper (I.e.) will show that they considered the common Haploplax 

 in South Australia conspecific with the Sydney shell, and separated their species 

 purely on colour characters and size. 



While colour markings may, in some measure, be distinctive of geographic 

 races, we are not justified in recognizing these features, unsupported by more 

 important characters, as having any specific value. 



A comparison of the extensive series in my collection from Port Jackson, 

 New South Wales ; Port Arthur and Frederick Henry Bay, south-eastern Tas- 

 mania ; Penguin, north-western Tasmania ; South Australia ; and from Yal- 

 lingup, in Western Australia, reveals some very interesting features. 



Size. — In respect to size, the Sydney shell averages decidedly smaller than 

 those from the other States; the largest from there, on my card, is 16X9 mm. 

 Those from north-western Tasmania and South Australia are very similar in 

 size, the largest on my cards measuring 23X13 and 20X1 1^ mm., respectively. 

 In Frederick Henry Bay, in south-eastern Tasmania, and Yallingup, Western 

 Australia, we find giant races measuring 30X1/^ and 29X1/ mm., respectively. 



Colour markings. — A very striking colour variety occurs at Port Jackson, 

 one in which the end valves are dark and the rest light, cream, white, or grey ; 

 and a similar varient also occurs in south-eastern Tasmania, but I am not avcare 

 of its occurring in any of the other localities named. 



The beautifully-streaked form described by Bednall and Matthews under 

 the name H. resplendens, seems only to occur in Victoria, South Australia, and 

 Western Australia. The cruciform variety in all its colour variations is common 

 to all the localities except Western Australia. 



In all the localities except this latter there exists a great variation both in 

 colour and pattern, but at Yallingup, on the west coast of the latter State, all the 

 specimens taken are of one colour pattern, a dark variety of the streaked form 

 named H. resplendens. 



Dr. Torr advises me that he also only collected this form in the same 

 locality, and the few specimens he collected on the south coast, at Albany, were 

 similar. 



