402 TEST ACE A ATLANTIC A. 



as the ' variety ' ; and I cannot but think, therefore, that 

 Mousson is hardly justified in adopting the opposite line, and 

 regarding the Morocco shell as the normal one. Be this how- 

 ever as it may, his diagnosis of the latter, as compared with the 

 Grand-Canarian one, is as follows : ' Paulo minor, solidior, 

 spira saepe irregulariter scalata, alba, seriatim corneo-maculata, 

 anfractibus supra planis, ad carinam crenulatam elevatis.' The 

 form from Grand Canary, on the other hand, he defines, under 

 the varietal name of ' canariensisj thus : ' Paulo major, spira 

 fere plana, interdum subscalata, corneo-grisea, infra indistincte 

 fasciata, anfractibus supra planiusculis, ad carinam non ascen- 

 dentem impressis.' 



Helix pulverulenta. 



Helix argonautula (pars, i. e. f. 13-15) [nee f. 16-18, nee 

 descriptionis] , d'Orb., in W. et B. Hist. 

 64. t. 2 (1839) 



pulverulenta, Lowe, Ann. Nat. Hist. vii. 107 (1861) 

 Pfeiff., Mon. Hel. v. 191 (1868) 



Mouss., Faun. Mai. des Can. 52. pi. 3. 



f. 10-12 (1872) 



Habitat Canariam Grandem ; ad El Charco, ultra Maspa- 

 lomas, sub lapidibus in saxosis aridis apricis, una cum H. 

 Despreauxii, d'Orb., degens, reperta. Necnon semifossilis 

 ibidem parce inveni. 



Although a little resembling it in primd facie aspect and 

 colouring, the present Helix is nevertheless exceedingly distinct 

 from the H. argonautula ; though it would appear to have 

 been confounded with it both by Webb and by d'Orbigny, inas- 

 much as three out of their six figures of the latter clearly 

 pertain, in reality, to this species, the other three, along with 

 the description, applying to the true H. argonautula. And, 

 so far as mere locality is concerned, it is not at all surprising 

 that they should have been in possession of both forms (even 

 whilst failing to observe their actual distinctions) ; for they 

 were obtained by Mr. Lowe and myself in almost adjoining 

 districts in the south of Grand Canary, and it is far from un- 

 natural therefore that the same consignment of orchil in which 

 the H. argonautula was found would contain likewise the 

 H. pulverulenta. Still it is inexplicable to me that, even if 

 Webb should have omitted to recognise in them more than the 

 exponents of a single species, their diagnostic characters should 

 have been subsequently overlooked by d'Orbignv, for. when 



