MADEIRAN GROUP. 183 



H. polymorpka (described by the Baron Paivaas his ' H. Pittce ') 

 descend to a still smaller statui-e, the ' var. poromphala ' does 

 nevertheless represent, on the average, a very much larger 

 and more robust shell than the present one. The H. tahellata 

 is also thinner, or less solid in substance, than most of these 

 immediate forms ; and I think that its specific separation 

 from the various races of the H. polymotpha is fully war- 

 ranted by the general peculiarity of its structure.' 



In the extreme flatness of its upper portion (the spire, 

 which is composed of only six whorls, being perfectly tabuli- 

 form) and the inflation of its base, causing the keel to be 

 ante-medial as well as prominently and very sharply expressed, 

 the H. tahellata has a prima facie aspect essentially its own ; 

 and, although somewhat fragile in substance, it is nevertheless 

 strongly sculptured, — it being much roughened with coarse irre- 

 gular subconfluent palish transverse lines, and besprinkled with 

 large palish granulations or tubercles. Its umbilicus is small, 

 but abriiptly and perpendicularly scooped-out (much after the 

 fashion of the ' var. attrita ' and the ' var. Gomesia7ia ' of the 

 H. polymorpjha) ; the margins of its peristome are wide apart and 

 well-nigh unconnected by an intervening lamina, the lower one 

 moreover being subflexuose and slightly recurved ; and in colour 

 it is of a dingy griseous- or yellowish-white, — either uni- or bi- 

 fasciate (or even efasciate) below, but very obscurely mottled 

 above with brownish and paler transverse markings, tlie former 

 of which so greatly predominate as to cause the surface to seem 

 at first sight to be (apart from the tubercles and lines) almost 

 uniformly brown. 



The H. tahellata, which appears to be peculiar to the south 

 of Madeira proper, was first detected, I believe, by Mr. Leacock, 

 on the dry maritime slopes of the Cabo Garajao, or Brazen Head ; 

 and it has subsequently been met with by Mr. Lowe, myself, and 

 others, in the same locality. The Baron Paiva records its occur- 

 rence also towards the Cabo Girao, to the tvestivard of Funchal. 



Helix testudinalis. 



Helix testudinalis, Loive, Ann. Nat. Hist. ix. 117 (1852) 



' The Baron Paiva (evidently copjang a somewhat hasty remark of Mr. 

 Lowe's) states that the //". tahellata is intimately related to the H. maderen- 

 sis, Wood ! ; but it is difficult to conceive any two species more utterly re- 

 moved from each other in all their characters, — the circular and elevated 

 peristome of the Placcntula section being sufficient even of itself to distin- 

 guish its members from those of the Biscula group. Although widely sepa- 

 rated from it specificallj^, perhaps the nearest ally of the I£. tahellata, both in 

 the structure of its umbilicus and the inflation of its under-parts, is tlie 

 Porto-Santan ' var. attrita- ' of the H. poli/morjflta ; but it has likewise a good 

 deal in common with the H. argonautula, W. ot B., of the Canarian archipelago. 



