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SOME MORE NOTES ON POLYPLACOPHORA. PART I. 



By Tom Ikedale. 



Read 17th April, 1914. 



Some time ago I contributed to these Proceedings some notes on 

 Polyplacoplioru (vol. ix, pp. 90-105 and pp. 1 53-62, 1910), and in 

 the last part (vol. xi, pp. 25-51, 1914) I furnished an account of the 

 Chiton Fauna of the Kermadec Islands. During the intervening years 

 I have accumulated some interesting notes, mostly on extra- Australian 

 forms, and a larger number of notes, dealing with Austi'alasian 

 material, I hope to incorporate in a review of the Australasian 

 Chiton Fauna I have in preparation. However, Dr. Thiele has 

 written me that he is now preparing a monograph of tlie Polyplaco- 

 phora for Das Tierreich, and 1 therefore consider it necessary that 

 my notes should be made available so that they may he criticized in 

 the production of Dr. Thiele's work. The succeeding notes are 

 mainly nomenclatural, but are of more than usual interest, while 

 some few are suggestive. 



Ckaspedochiton (Thaumastochiton) MOBiusr, Thiele. 



In the Report on the Marine MoUusca obtained by J. Stanley 

 Gardiner among the Islands of the Indian Ocean (Trans. Linn. Soc. 

 Ljnd., vol. xiii, p. 119, 1909) Melvill recorded — 



" 357. Acanthocifes [Lohoplax) laqiieatus (Sowb.). 

 Loc. Amirantes : Station E 13, 20 to 25 fathoms, calcareous rubble." 



The specimen upon which this record is based is now in the 

 British Museum, and at the first glance it seemed quite distinct from 

 Sowerby's laqiteatus. The shell is curled, and approximately measures 

 38 mm. X 15 mm. The girdle is produced in front and narrowed 

 behind, and could be termed leathery, minutely sandy. Four pores 

 are clearly observed before the head-valve, and seven at the sutures, 

 and a peculiar feature is their presence behind the tail-valve. Here, 

 apparently protected by the curling, the tufts are preserved, as is 

 also a peripheral fringe, consisting in each case of long opaque-white 

 spicules. The colour of the girdle is bright puce pink. The head- 

 valve is sculptured with seven elevated ribs, the outside ones con- 

 stituting the border. 1 note this, as in Lohoplax usually only five 

 ribs are indicated, no outside ones being developed. These ribs are 

 not differentiated in any way, but appear simply as undulating 

 elevations. The sculpture consists of rounded sepai'ated pustules of 

 varied sizes. The lateral areas of the median valves are well raised, 

 the sculpture consisting of rounded pustules closely packed ; the 

 median areas are covered with oval flat-topped pustules which become 

 confused and merged into a continuous flattened rib on the jugum. 

 The tail-valve is long, the mucro posterior, very much elevated and 

 recurved, then sloping backward, making a convex lateral area. I have 



VOL. XI.— JUNE, 1914. 9 



