56 HELICIDE. 
Var. Il. Helmii. Like Var. I., but pearl white. 
o Z. PURUS (clear). 
Compressed, extremely thin, dull, semi-transparent, light 
brown horn-colour; very faintly striated in both directions, 
and having consequently a reticulated appearance under @ 
microscope; whorls four, the last very large; mouth almost 
circular; wmbilicus rather narrow, but deep; diameter nearly 
one-seventh of an inch. 
Found in many parts of Great Britam and Ireland, 
but not everywhere. It is a very fragile shell, and the 
animal is difficult to extract entire. 
The variety is an exquisitely delicate object. 
The animal is cream-coloured. 
Var. margaritacea. Pearl white and nearly trans- 
parent. 
6. Z. RADIATULUS (slightly rayed). 
In size and shape resembling the last species, but highly 
glossy; darker in colour, and exquisitely marked by 
regular curved strize in the line of growth—more strongly 
above than below; whorls four and a half; diameter nearly 
one-seventh of an inch. 
Dr. Jeffreys says that this species frequents moister 
places than Z. purus. It isnot abundant though widely 
distributed in Great Britain and Ireland. Under a 
lens it is a beautiful object, and when once seen need 
never be mistaken for the last species, but care should 
