CANARIAN GROUP. 391 



anything else with which I am acquainted ; nevertheless it is 

 smaller and less opake than that species, as also very much more 

 flattened on the upper side (its spire being almost as much 

 depressed as in the H. planaria), but a little more convex 

 and inflated beneath, causing the umbilicus, which is appreci- 

 ably narrower, to be more suddenly, or abruptly, scooped- out. 

 Its keel, too, is more acute, and a little more evidently com- 

 pressed both above and below ; and the margins of its peristome 

 are relatively wider apart. 



Helix planaria. 



Carocolla planaria, Lam., Hist. vi. 99 (1822) 



Helix afficta, var. planaria, Mouss., Faun. Mai. des Can. 65 



(1872) 



Pfei/., Mon. Eel. vii. 296 



(1876) 



Habitat Teneriffam ; in montibus supra et ultra Taganana 

 degens. 



The H. planaria of Teneriffe, the afficta of Palma, and 

 the discobolus of Gromera, in their general structure and 

 practically bald surface, as well as in the sudden and somewhat 

 angular scooping-out of their perpendicular-sided umbilicus, 

 may be regarded as representative forms ; but whether it be 

 desirable to treat them as insular modifications or as separate 

 species I am scarcely prepared to say. Perhaps either view is 

 equally tenable ; for as it is pretty clear that they can never be 

 absolutely connected by intermediate links, it is impossible to 

 pronounce for certain that they are merely developments of a 

 single type. At any rate they each stand in precisely the same 

 relation to each other ; and it seems unreasonable therefore to 

 cite the planaria (as Mousson has done) as a variety of the 

 afficta, and yet to retain the latter as specifically distinct from 

 the discobolus. Whichever principle we adopt should be ap- 

 plied equally to them all ; and since at any rate the afficta and 

 discobolus have always been looked upon as properly-defined 

 species, I am inclined to be guided by that assumption, and to 

 extend it to Lamarck's H. planaria, which, if anything, is 

 perhaps the best characterised of the three. 



It was only on the mountains in the north-east of Teneriffe, 

 above and beyond Taganana, that we met with the H. planaria ; 

 and it appears to have been found in the same district by 

 Fritsch and Reiss. The particular spot in which Mr. Lowe 

 subsequently obtained it was on a hill called ' Benijo,' between 

 Taganana and Point Anaga. It is at once separated from its 

 Gromeran and Palman allies by its extremely flattened and very 



