Rev. R. T. Lowe on a new Species of Helix. 95 



column at p. xiv., aud adding Cyclostoma flavescens, Lowe, to 

 both columns. 



Thus the apparently extinct or yet undiscovered living shells 

 of Cani9al will now stand to the recent of the same deposit in 

 the diminished ratio of 9 to 36 or 39, i. e, of 1 to 4 or 4^, 

 i. e. 25 per cent, exactly, or 23J very nearly. 



But if the fossil shells of the entire Madeiran group, consist- 

 ing of Madeira, Porto Santo, and the three Desertas, be regarded 

 as one whole, it is evident, from the facts above mentioned, that 

 the proportion between the apparently extinct and recent shells 

 in these deposits, considered jointly, will be much more con- 

 siderably reduced than it appears in the above corrected list 

 confined to Madeira proper. For thus, in fact, there will remain 

 no characteristic or conspicuous fossil shell undiscovered recent, 

 except H. delphinulttj which, however, may itself be reasonably 

 expected to reward, with the few other minuter species, the close 

 researches of some future naturalist. 



3. Helix tetrica, Paiva. 



T. supra nigricans vel latissime nigro fasciata, depresso-discoidea, sub- 

 planata, carinata, solida, undique confertissime granulis distinctis- 

 simis albidis prominentibus grosse scobinata ; carina acuta, expres- 

 siuscula, vix limbata, subsupera ; spira convexo-depressa, subpla- 

 nata, pulvinata, sc. anfractui ult. antice tumidulo superimposita ; 

 anfractibus convexiusculis, penultimo antice subdepresso, sutura 

 distincta ; umbil. maximo, aperto, patulo, spirali, ^ diam. maj, 

 latitudine aequante. 



Diam. maj. 13-15, min. 11-12, alt. 7-8 mill; anfr. 7-8. 



Hab. in ins. Deserta Australi in prseruptis excelsis maritimis "inter 

 lichenes." 



A fine and certainly new species of the H. polymorpha tribe, 

 very distinct from H. senilis /8*, to which, when sent to me 

 last year by the Barao de Paiva, I at first referred it, by reason 

 of its large wide open umbilicus and much coarser granulations. 

 In both these points, with the addition of its flattened discoidal 

 shape, it is also quite distinct from H. polymorpha or H, pulvi- 

 nata. A few examples were found by a man collecting for the 

 Baron " on the S. Deserta, or Bugio, amongst lichens on the sea- 

 clifi"s,^' in the spring of 1861. The colouring is precisely that 

 of H. polymorpha, var. p. nigricans , subvar. 1 or 3, — viz. dark 

 coffee-brown above, relieved only in two of the four specimens 

 before me by a pale line along the keel and suture. Beneath, 



* Lowe, Syn. Diagn. in Ann. and Mag. ser. 2. vol. ix. p. 116; and Catal. 

 Moll. Mad. in Proc. Zool. Soc. (1854), part xxii. p. 189. Supposing, how- 

 ever, H. senilis, Morelet, in Joum. de Conch. (1851) ii. 353, to be a good 

 species, H. senilis, Lowe, must be changed into H. salebrosa. 



