ASHBY : NOTES ON THE GENUS STENOCHITON. 261 



The characters differentiating these shells from any other known 

 forms are undoubtedly developed as a result of their peculiar 

 environment. 



The publication of the writer's monograph on this genus in 1918 

 has led to the discovery of several of these forms in large numbers, 

 and he was himself able in 1920, on the occasion of a brief visit to 

 Western Australia, to extend their known range westward for about 

 3,000 miles of coast line. He can truthfully say that since under- 

 standing the habits of these Stenochitons he has been able to find the 

 species known as S. cymodocealis, Ashby, in every locality he has 

 visited in South and West Australia where the sea-grass Cymodocea 

 occurs. 



As representatives of sea-grasses are found in suitable localities 

 throughout the world, it will be quite safe to assume that repre- 

 sentatives of this genus or some kindred form should be found in 

 all these localities when properly searched for. 



Stenochiton longicymba, Blainville, 1825. 



(= S. juloides, Ad. and Aug., Proc. Zool. Soc, 1864, p. 193 ; loc. cit., 



1865, p. 58, pi. xi, f. 15. Angas, Proc. Zool. Soc, 1865, p. 188,= 



S. juloides, Ad. and Aug., of Pilsbry (Man. Con., vol. xiv, p. 55), 



non J schnochiton longicyniba, Quoy et Gaimard, auct. = S. 



jidoides, Ad. and Ang., of Ashby (Trans. Roy. Soc. of S. Austr., 



xlii, 1918, and Journ. and Proc. Roy. Soc. of W. Austr., vol. vi, 



pt. 2, 1919-20), Auct.) 



Messrs. Iredale and May in their paper " Misnamed Tasmanian 



Chitons " (Proc. Malac. Soc, vol. xii, Nov., 1916, p. 105), state with 



regard to Rochebrune's Schizochiton nympha (Bull. Soc Philom. Paris, 



Ser. vii, tom. viii, 1884, p. 36), from King Island, collected by Peron 



and Lesueur, that from Dr. Thiele's description and figure : " There 



is certainty that Rochebrune renamed the Blainvillean species, and 



that Chiton longicyniba, Blainville, is a Stenochiton. Thiele does not 



definitely make this a synonym of Stenochiton juloides, Ad. and Aug., 



and until King Island specimens are again collected, we prefer to 



allow Stenochiton longicymba (Blainville) as a separate species." 



During the first week of August last (1922) I had, through the 

 courtesy of Dr. Lamy, an opportunity of examining the collections 

 of Polyplacophora in the Museum d'Histoire Naturelle in Paris. 



Rochebrune's type of his Schizochiton nympha was on a card, and 

 I am delighted to be able to confirm Messrs. Iredale and May's 

 surmise that it is the lost type of Blainville's Chiton longicymba, 

 and. that it is a Stenochiton. I have not the slightest hesitation in 

 stating that it is quite a typical shell of the species that was described 

 by Adams and Angas under the name of Stenochiton juloides 

 in 1864. 



The type is mounted on a card, measures 32 by 6 mm., girdle 

 absent. It is a typical specimen of the shell known as S. juloides, 



