The Rediscovery of Choriplax ( microplaxj grayi, 

 adams and angas (order po lyplacoph o ra, with 

 notes on its true place in the natural system 

 and the description of a new sub-species. 



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



[Bead July 14, 1921.] 



Plate IX. 



Microplax grayi, H. Ad. >and Aug., P.Z.S., 1864, p. 194; 

 I.e., 1865, p. 58, t. 11, f. 16. Angas, P.Z.S., 1867, p. 224. 

 Carpenter, MS., p. 12. Pilsbry, Man. of Con., vol. xiv., p. 21. 



Choriplax grayi, H. Ad. and Ang. Pilsbry, Nautilus, vii., 

 p. 139, 1894. Thiele, Rev. des Sys. der Chitonen. Zool., iv., 1910. 



It is with pleasure that I acknowledge my indebtedness 

 to Dr. W. G. Torr for the opportunity of examining and 

 describing one of the most interesting chitons it has been 

 my privilege to examine. On May 7 last I received from 

 him a few chitons for identification, all taken by Mr. George 

 Pattison, near Cape Banks Lighthouse. One, he said, was 

 not only a species new to him, but also belonged to a genus 

 he had never seen before. I saw at once that the specimen 

 was a remarkable find, evidently' related to the genus 

 Amicula, a genus whose habitat is in the cold waters of the 

 North Pacific, from the Okhotosk Sea to the Behring Sea, 

 and in corresponding latitudes on the eastern side of the 

 North American continent. 



Genus Microplax, Adams and Angas, 1864. Original 

 description: — "Insertion plates smooth and thin, present in 

 all the valves. Sutural plates obsolete, the sinus extremely 

 shallow. Girdle thin, horny, most minutely granulous. 

 Valves largely concealed in the girdle, the exposed portions 

 small and separated. 



"In the present genus a small portion only of each valve 

 is exposed, and the sutural plates and sinus are obsolete. No 

 other chiton having unslit insertion plates approaches this 

 remarkable group." 



M. grayi, Adams and Angas. Original description : — 

 "Shell elongated, convex, brown; exposed portion of the 

 valves minute, wide heart-shaped, carinated, strongly granu- 

 lated, the intervals between the exposed parts of the valves 

 about as long as the latter. Lateral areas defined by a dis- 

 tinct rib. Girdle moderate, corneous, smooth. Length, 

 13; width, 5 mill. Sydney Harbour, Australia; under stones 

 at low water." 



