174 TEST ACE A ATLANTIC A. 



It is only on the Desertas that the present race of the H. poly- 

 morpha has been found ; and although it occurs on the whole 

 three of them, it is principally on the northern and southern 

 islands that it abounds, the ' /3. salebrosa ' being the dominant 

 form in the Deserta Grande. There is, however, very little differ- 

 ence between that modification and the present one, the much 

 smaller umbilicus of the ' 7. poromphala ' being its main distinc- 

 tive feature ; though it is likewise, on the average, a smaller shell 

 altogether, descending on the Bugio (where it was also found in a 

 subfossilised condition, by Mr. Lowe and myself, during June of 

 1855) to a comparatively diminutive stature, the most reduced 

 examples measuring only about four lines across their broadest 

 part. 



S. Pitta?, Paiva. 



Helix senilis, var. 7., pusilla, Lowe, Proc. Zool. Soc. Lond. 



189 (1854) 

 Pittae, Paiva, Journ. de Conch, xiv. 340 t. 11. f. 5 



(1866) 



Id., Mon. Moll. Mad. 41. t. 1. f. 3 (1867) 

 polymorpha, /3. (subv. 2. minor), Id., ibid. 85 (1867) 

 ' Pittse, Pfeiff., Mon. Ed. vii. 352 (1876) 



Habitat Desertam Australem : prsesertim in statu semifossili 

 (an vere recens ?) occurrens. 



This is the most minute form under which the H. polymor- 

 pha has hitherto been ascertained to exist, the examples measur- 

 ing only from about 3 to 3^ lines across their broadest part ; and it 

 is one which seems to be peculiar to the Southern Deserta, where 

 it was met with by Mr. Lowe and myself, during June of 1855, 

 and from whence it has subsequently been obtained by the Baron 

 Paiva. 1 But it was only subfossilized that we found it ; and I 

 have no evidence hitherto that it occurs in a living state, for it is 

 almost certain that the individual from which the Baron (I. c. 85) 

 professed to describe the ' animal ' was merely a small one of the 

 common ' 7. poromphala? This variety however seems to differ 

 in no respect (either as regards sculpture or relative proportions) 

 from the c 7. poromphala ' (though its worn and colourless con- 

 dition may give it at first sight a somewhat peculiar aspect) ex- 

 cept in its extremely reduced stature, and in its possessing only 6^- 



1 The Baron therefore was not altogether accurate in adding, concerning 

 this particular variety, ' In Deserta Australi a meipso primum inventa ; ' for, 

 in the first place, it was found by Mr. Lowe and myself more than ten years 

 previously, and, in the second place,. it is well known that he never collected 

 on the Desert as at all, his material having simply been brought to him by 

 men, not always very trustworthy, whom he sent out from Funchal. 



