112 TESTACEA ATLANTICA. 



anterior portion also of the large basal whorl (immediately 

 below the suture) is diluted in colouring, being almost as pallid 

 as the umbilical region ; in which case the ultimate whorl may 

 be defined as bifasciate, two dark bands being shaped-out, 

 instead of a single central pale one. Apart from mere orna- 

 mentation, the H. punctulata is (like the Bowdichiana) glo- 

 bose and compact in contour, with its small chink-shaped 

 perforation very nearly closed over, and with its surface (which 

 is covered with irregular oblique lines, or slight plicae) studded 

 with asperated punctures, out of each of which, except in old 

 and worn examples, a minute bristle will be seen (when viewed 

 beneath a high magnifying power) to proceed. 



As already mentioned, the H. punctulata is a most abun- 

 dant shell in Porto Santo (and the immediately adjacent islets), 

 where it is generally distributed, occurring beneath stones, 

 and often coating itself with a hard layer of the dry dusty soil ; 

 but in Madeira proper (where the closely-allied H. Bowdich- 

 iana swarms in the subfossiliferous deposits at Canipal) it does 

 not appear to occur, nor indeed are there any traces of its 

 having ever occurred there. On the Southern Deserta however 

 (where there are no indications of the extinct H. Bowdichiana) 

 it is far from uncommon ; and that it is not a recent intro- 

 duction on that remote rock (brought about by some accidental 

 means, as might perhaps be supposed, from Porto Santo) is 

 proved to a demonstration by the twofold fact that it is found 

 there in a subfossil condition (as well as recent), and that it 

 also assumes a slight local modification (unimportant in itself 

 except topographically) which is just sufficient to enable us to 

 recognize it as an insular race. 



The examples referred to, from the Southern Deserta (or 

 Bugio), are on the average a little smaller than the Porto- 

 Santan ones, with their spire relatively a trifle more exserted or 

 raised, and with their surface, if anything, somewhat more 

 setose or hispid ; their substance, too, is very thin. This 

 slight insular phasis was defined by Mr. Lowe as the 'var. a. 

 avellana.' 



( EuparypJia, Hartm.) 



Helix pisana. 



Helix pisana, Mull., Verm. Hist. ii. 60 (1774) 



Lowe, Cambr. Phil. S, Trans, iv. 52 (1831) 



., W. et B., Ann. des Sc. Nat. 28. 6 (1833) 



d'Orb., in W. et B. Hist. 58 (1839) 



Lowe, Proc. Zool. Soc. Lond. 171 (1854) 



Alb., Mai. Mad. 21. t. 3. f. 1-18 (1854) 



Paiva, Mon. Moll. Mad. 70 (1867) 



