386 TEST ACE A ATLANTIC A. 



the sea), that I originally met with it, though merely two 

 examples, and those in an immature condition. But it subse- 

 quently occurred to me, in much greater abundance, at an 

 altitude of about 9,000 feet, in Teneriffe, namely amongst the 

 dead sticks and rubbish which had accumulated beneath the 

 bushes of the 'Retama' (or Canarian Broom), on the Cumbre 

 above Ycod el Alto, for which that 1 fty region is so celebrated ; 

 and since I likewise took it, under precisely similar conditions, 

 on the opposite Cumbre, above the Agua Mansa, the species 

 may perhaps be defined as occupying more particularly the 

 upland scoriaceous districts which are characterized by the 

 Eetamas. 



Although so remarkable in its habitat, the present Helix is 

 a most inconspicuous, depresso-rotundate little species (mature 

 individuals measuring only about 2 lines across their widest 

 part) ; and indeed whatever peculiarities it may possess are 

 well-nigh obscured by the habit which it has of coating itself 

 over with a covering of dirt. Moreover the excessive thinness, 

 and flexibility, of the shell renders this outer envelope extremely 

 difficult to be removed without at the same time destroying the 

 clothing, and occasionally also even the cuticle; but when it 

 has been sufficiently got rid of to permit the various features to 

 become visible, the H. pavida will be seen to be of a pale 

 yellowish- (or often olivaceous-) horny-brown, semitransparent 

 in substance, but with its surface (which is nearly opake, and 

 finely sculptured with subconfluent transverse lines) studded all 

 over with most 'minute and very abbreviated, but rather remote, 

 silvery squamiform bristles, which give it, when the specimens 

 are unrubbed, a slightly frosted appearance ; and, although at 

 times quite unicolorous, it has more frequently a curious ten- 

 dency to have its dorsal region (though nearly destitute of a 

 keel) marked with a few unequal, detached, paler, yellowish- 

 white blotches, representing a fragmentary fascia. Its um- 

 bilicus, in proportion to the size of the shell, is rather large and 

 open ; its volutions are a little convex, with the suture a good 

 deal sunken; and its peristome is acute, with the upper and 

 lower margins unconnected and wide apart. 



The two Palman examples of this shell, to which allusion 

 has already been made, have always appeared to me to be abso- 

 lutely conspecific with the Teneriffan ones, and such likewise 

 was the opinion (judging from their general fades, and the un- 

 mistakeable peculiarity of their habitat) of Mr. Lowe ; yet 

 Mousson has described them, although confessedly immature 

 and unsatisfactory, as a new species, under the title of ' H. 

 pavida.' But their characters, to which he calls attention in 

 his diagnosis, are simply, and purely, those of the ordinary H. 



