THE NAUTILUS. 135 



Helix hortensis. The one I take as typical of the variety meas- 

 ures 16 by 20 mm., and the apex, with curved rows of granules, 

 is delicately tinted with orange, giving the shell a more recent 

 appearance than usual. This may be the latest phase of bow- 

 ditchiana, but its resemblance in form to more ordinary snails 

 might be taken to indicate greater antiquity. I was not able to 

 make out distinct zones in the Porto Santo fossil beds, although 

 some species abound in one place, and are rare or absent else- 

 where. The sandy deposits are broken down by the weather, 

 and the shells loosened upon the surface. Many of these are 

 again covered, as the wind blows the sand, and the lime again 

 cements the deposit, so that it is quite possible to find shells of 

 entirely different ages mixed together. In fact the very modern 

 H. pisana is being thus incorporated, and no doubt in years to 

 come it will be possible to dig pisana and bowditchiana out of 

 the same fossil-beds, just as if they had been strictly contem- 

 poraneous. 



In order to show the greater uniformity in the Canigal P. 

 bowditchiana, I give the measurements of 156 shells, citing the 

 two dimensions as before. 18.19 (1), 18.21 (1), 19.20 (2), 

 19.21 (7), 20.20 (6), 20.21 (18), 20.22 (8), 21.21 (9), 21.22 

 (22), 21.23 (7), 21.24 (3), 22.21 (1), 22.22 (12), 22.23 (28), 

 22.24 (2), 23.22 (1), 23.23 (5), 23.24 (13), 23.25 (1), 24.22 

 (1), 24.24 (2), 24.25 (4), 26.25 (1). 



The nearest living relative of P. bowditchiana is P. punctulata 

 (Sowerby), exceedingly common on Porto Santo, and found 

 also on the outlying islets, even the isolated Ilheo de Nordeste. 

 It hides under rocks, more or less buried in the ground, and I 

 never saw it crawling abroad. A remarkable feature is the 

 opaque white mantle, which, when the animal is within the 

 shell, looks at first sight like a dense white epiphragm. The 

 genitalia show a very long slender flagellum. The living ani- 

 mal may be described as follows : Animal whitish translucent ; 

 tentacles and neck above dark grey, nearly black ; foot very 

 broad, caudal end very broad and flat ; a large black mark on 

 each side posterior to tentacles ; mantle opaque white (speci- 

 men from Villa Baleira). The shells vary much in color, some 

 being very dark. Two bands, never seen in bowditchiana, are 



