'rOMLIN : ON XYLOPHAGA PR^STANS, SMITH. 73 



and while closed during retraction of the animal the spaces between 

 the palatal plicae are sufficient to admit air for breathing purposes. 

 This peculiar sliding action of the clausilium I have not seen referred 

 to by any previous author,^ which may possibly be explained by the 

 fact that the species which have served as a basis of investigation 

 are rather small, and their examination is consequently somewhat 

 difficult. This difficulty may be overcome by utilizing some of the 

 larger Japanese forms — such as C. martensi, Herkl., and C. valida, 

 Pfr. Five species belonging to the Palsearctic subgenus Alopia are 

 without clausilium. 



This completes our survey of the various groups of land mollusca 

 furnished with armature. 



NOTE ON XYLOPHAGA PR M ST AN S, SMITH. 

 By J. R. Le B. Tomlin, M.A., F.E.S. 

 Read \2th March, 1920. 

 This species was described in these "Proceedings" (vol. v, p. 328). 

 I am now able to give more definite details as to its habitat, and the 

 following notes are written by Capt. J. H. Walker, the master of 

 a trawler, who was the original discoverer, in a letter received 

 28th October, 1919 :— 



"I have taken this shell off the Durham and Northumberland 

 coast in various depths of water from 25 to 45 fathoms on five or 

 six occasions, and always on pitchpine logs or masts that had 

 been a long time in the water. I used to split the wood with wedges 

 and take the shell out alive and keep it alive in water for several 

 days. 



" I noticed the animal was white with a fairly long siphon. 

 I kept them in a 2 lb. glass jam-jar filled with water, and the animals 

 could reach the surface of the water (about 4 inches), except the very 

 smallest. 



" I found they always bored across the grain of the wood in 

 a perpendicular direction, and the larger the shell the deeper the 

 cavity, 



" On the top surface of the log or mast there was nothing to 

 indicate the presence of shells except a number of very small holes 

 like pin-holes. 



" My largest specimens are fully 1\ inches in diameter, whilst my 

 largest X. dorsalis is only f in. in diameter. I always found 

 X. dorsalis in hard wood, oak, elm, or teak. 



" Some of the largest specimens of X. 'proestans had bored Q\ inches 

 into the wood (by actual measurement). The animals are phos- 

 phorescent at night." 



^ 1 first drew attention to this fact in the Fauna of British IndiQ,, Mollusca, 

 vol. ii, 1914, p. 304, and my observations on that occasion have here been 

 embodied. 



