CANAKIAN GROUP. 373 



have more the aspect, I think, of the var. geminata than of the 

 pisana proper ; though their perforation is by no means quite 

 concealed. 



The variations in mere colour of this protean Helix are so 

 endless (scarcely two specimens, except the totally white ones, 

 being exactly alike) that it would be almost a waste of space to 

 attempt to tabulate them. 



Helix impugnata. 



Helix plana ta (pars), W. et B. [nee Ghemn.~\, Ann. ties So. 



Nat. 28. syn. 312 (1833) 

 „ pisana monstrosa (pars), cVOrb., in W. et B. Hist. 59 



(1839) 

 „ impugnata, Mouss., Schw. Denksch. xv. 132 (1857) 

 „ „ Id., Faun. Mai. des Can. 32. pi. 2. f. 35, 



36 (1872) 

 „ „ Pfeiff., Mon. Hel. vii. 248 (1876) 



Habitat Lanzarotam, et ins. parvam adjacentem ' Graciosa ' 

 dictam ; ad rupes maritimas circa oram borealem, vidgaris. 

 Etiam semifossilis a cl. Mousson occurrere dicitur. 



This species, which has been observed hitherto only in the 

 north of Lanzarote, was mixed up by Webb with the (equally 

 depressed, but otherwise dissimilar) var. Grasseti of the pisana, 

 from the Isleta of Grand Canary, — the two together (as is evi- 

 dent from his habitat in ' Canaria, Lancerotta, et Gfraciosa ') 

 being referred to the H. planata, Chemn. ; and thus a double 

 error was placed on record, — for not only are the Lanzarotan 

 and Canarian shells distinct inter se, but neither the one nor 

 the other of them accords with Chemnitz's species, which is 

 totally different and belongs to the fauna of Morocco. 1 The 

 present Helix was first defined by Mousson, in 1857, from Lan- 

 zarotan examples which were collected by M. Hartung, who is 

 said to have also met with it in a subfossil condition. 



The H. impugnata was taken in profusion by Mr. Lowe and 

 myself in the extreme north of Lanzarote, particularly about 

 Chache and the lofty maritime cliffs (overlooking the Salinas) 

 known as the Risco ; and we likewise obtained it on the little 

 adjacent island of Graciosa. 



There can be no question that the H. impugnata belongs 

 strictly to the pisana-ty\*e, and that the variety of the shell 

 which is less acutely keeled (the ' var. subgeminata ' of Mous- 

 son) makes a very decided approach towards the ' var. Grasseti ' 

 of the pisana, which occurs in Grand Canary. Nevertheless, in 



1 The true If. planata, Chemn., is abundant around Mogador, where it 

 may be found adhering to the shrubs of Broom (Retama nwnosperma, L.). 



