142 



-examination of the soft parts may reveal ? So naturally does 

 this genus seem to fit into the place I have assigned to it, 

 that the wiser course might possibly be to place both Choriplax 

 and Cryptochiton under the Family Acanthochitidae, Pils., 

 and drop the Subfamily Cryptocbitoninae. 



Note. — In the writer's last paper on Australian Poly- 

 placophora (Trans. Roy. Soc. S. Austr., vol. xliv., p. 286, 

 1920) reference is made to the race of Callistochiton meri- 

 dionalis, Ashby, which had been previously described from 

 a single specimen from North-west Tasmania, and to which 

 he had attached the name of mayi. Since this was written 

 several specimens from the same district have come to hand, 

 and while some show the same backward habit of developing 

 the typical network sculpture that was noted in the paper 

 referred to, other specimens are almost normal. Had more 

 material been available at the time the then unique specimen 

 was described, the writer would have contented himself with 

 simply noting the fact that shells from this North-west Tas- 

 manian coast attain the adult characters more slowly than is 

 the case with those from the type locality in South Australia. 

 In the same paper, p. 283, Lepidopleurus inquinatns, should 

 be of Reeve, and not Blainville, as printed, and L. cat en at us, 

 Hed. and Hull, should have been withdrawn from the Aus- 

 tralian fauna, it being a Lord Howe Island species. 



Addendum. — Since presenting the foregoing paper I have 

 had the opportunity of reading in the Nautilus, vii., p. 139, 

 Dr. Pilsbry's note attached to his proposed substitution of 

 the name Choriplax for that of Microplax, which name was 

 preoccupied, and I now quote his remarks in full: — "This is 

 an extremely peculiar and isolated genus, and forming, I am 

 disposed to believe, a distinct family of the Eoplacophora, or 

 slitless chitons; that is, if the slits really prove to be com- 

 pletely absent, for the unique type has not been disarticulated. 

 In some features it recalls the Acanthochitidae. The single 

 specimen was described and illustrated from the unique type 

 in the British Museum, in the Manual of Conchology, vol. 

 xiv." 



DESCRIPTION OF PLATE IX. 



Fig. la. Choriplax grayi pattisoni, Ashby, upper side, x about 5. 



Showing small heart-shape tegmentum and enveloping 



epidermis with tear in valve 2 revealing smooth articula- 



mentum underneath. 

 Fig. 16. Choriplax grayi pattisoni, Ashby, interior of shell, 



x5. Showing sutural laminae. 

 Fig. lc. Choriplax grayi pattisoni, Ashby, upper side with strong 



light thrown through the shell showing (a) shadow of 



sutural laminae, (b) opacity of tegmentum, (c) the posterior 



lobes united across the median line, xo. 



