157 



phora are easily separated. The zigzag markings of albida 

 (? petholata), the smooth reticulated markings of costata 

 (? glauca), and the strongly raised nodules of the lateral area 

 in matthewsi (? conspersa) make the separation easy except 

 in worn specimens. 



Mr. Gatliffe, of Victoria, has taken considerable pains 

 in identifying the Plaxiphora, and agrees with Dr. Thiele in 

 identifying our P. ylauca with P. albida, Blainville. 



P. albida is often found at and above high-water mark, 

 and generally adheres to one spot without moving about like 

 other chitons. At Robe I have seen hundreds alive, blistering 

 in the sun. I have collected it all around the coast of South 

 Australia, from Port MacDonnell to Streaky Bay, as well as 

 Queensland, Victoria, and Tasmania. Going out from Streaky 

 Bay 40 miles to St. Francis Island, P. costata takes the place 

 of albida, and that would seem to continue right on to Wes- 

 tern Australia, for I obtained costata at Albany, Bunbury, 

 Rottnest Island, and saw nothing of albida. 



I don't know if pearls are often found in chitons, but 

 I extracted a blue egg-shaped pearly substance from the 

 interior edge of a Plaxiphora albida. 



39. Plaxiphora matthewsi, Iredale, 1910. 



Plaxiphora conspersa, non Adams and Angas : Bednall, 

 Proc. Mai. Soc, London, 1897, vol. ii., p. 154. 



P. matthewsi, Iredale, Proc. Mai. Soc, London, vol. ix., part 

 ii., June, 1910, p. 99. 



This is the rarest of South Australian Plaxiphora. It 

 is found in deeper water than either albida or costata. Its 

 great breadth in proportion to its length easily distinguishes 

 it from either of these. I have specimens from Marino, Trou- 

 bridge, Second Valley, and St. Francis Island. I have also 

 collected it on the north-west coast of Tasmania. Iredale 's 

 description, loc. cit., is very good, but the absence of plates 

 is a hindrance to identification. 



The description of Chcetopleura conspersa, Adams and 

 Angas, P.Z.S., 1864, p. 193; Angas, P.Z.S., 1865, p. 187, 

 agrees so well with matthewsi that I place it under a new 

 nomenclature with considerable diffidence. 



A very pretty half -grown specimen was taken by Mr. F. 

 L. Saunders at Port Noarlunga. The nodules on the lateral 

 areas are like tear-drops. 



40. Plaxiphora, costata, Blainville. 



Chiton costatus, Blainville, Diet. Sc. Nat., xxxvi., p. 548; 

 Pilsbry, Man. Conch., vol. xv., p. 105. 



C. glaucus, Quoy and Gaimard, Voy. "Astrolabe," Zool., iii., 

 p. 376. 



