CAN AM AN GROUP. 403 



viewed carefully together, it seems well-nigh impossible to 

 mistake them. 



The H. joulverulenta is a good deal smaller than the argo- 

 nautula (measuring only 3 lines across its widest part), and it 

 is very much less sharply carinated, — the keel, moreover, which 

 is comparatively simple (or nearly uncrenulated), being less 

 broadly compressed (or flattened-out) on the upper side ; both 

 its spire and volutions are rather more convex ; its suture is 

 more sunken or impressed, without any appearance of a thread- 

 like keel at its upper edge ; its ultimate whorl is narrower ; its 

 costate lines are considerably finer and less undulated ; its basal 

 region, although inflated, is less conically convex ; its umbilicus 

 is smaller; its aperture is much less angular, with the margins 

 of the peristome more completely disconnected by an interven- 

 ing lamina ; and the fascia of its underside is usually brighter 

 and more developed. 



It was in the dry and stony district of El Charco, beyond 

 the sandy wastes of Maspalomas, in the extreme south of Grand 

 Canary, that the H. pulverulerita was met with by Mr. Lowe 

 and myself; and as that region is at no great distance from 

 Arguineguin, the locality in which we found the H. argonau- 

 tula, it is extremely probable that the gradually acquired areas 

 of the two species approach each other very closely, even if they 

 do not indeed absolutely overlap. We also obtained the H. 

 pulverulerita in what I cannot but think is a truly subfossilized 

 state, in the immediate vicinity of its present habitat. 



Helix granostriata. 



Helix granostriata, Mouss., Schiv. Denksch. xv. 135 (1857) 

 „ „ Id., Faun. MaL des Can. pi. 3. f. 13-15 



(1872) 

 „ Pfeiff., Mon. Eel. vii. 245 (1876) 



Habitat Lanzarotam, et Fuerteventuram ; in ilia recens, sed 

 in hac nunc recens nunc semifossilis reperitur. 



Three examples of this species are now before me which 

 were given to Mr. Lowe in 1855 by M. Hartung, by whom they 

 had been taken in Fuerteventura ; and were it not for the com- 

 parative largeness of their umbilicus, I should perhaps have been 

 more inclined to refer the H. granostriata to the Turricula 

 group than to Discula. As it is, however, I think that its 

 affinities are more with the argonautula and pulverulerita 

 than they are with the forms around the Despreauxii and mi- 

 randos. 



The present Helix is perhaps a trifle larger, on the average, 

 than the H. argonautula (measuring about 4 lines across its widest 



D D 2 



