104 PUPIDA. 
Genus.—BALEA Prideaux. 
Shell sinistral, turriculate, thin, finely striated and streaked with 
white in the line of growth. 
B. PERVERSA (turned the wrong way) Linne. PI. V., f. 5. 
Sinistral, club-shaped, thin, dark horn-colour, semi-transparent, 
glossy, closely striated in the line of growth; whor/s 7—8; mouth 
squarish oval, sometimes furnished with a denticle on the columella; 
outer lip thin; zdz7icus narrow. A. 7mm. B. 25 mm. 
This shell though local is abundant where it occurs. 
Its distribution is very wide, extending over the whole 
of Great Britain. In Ireland it is locally abundant and 
has a wide range. It is found chiefly on the bark of trees; 
Dr. Jeffreys says:—‘‘chiefly the beech, ash, sycamore and 
apple.” I once found it ona willow near Maidenhead, in 
company with CZ. dzdentata, the young of which it much 
resembles. This resemblance it is necessary to note or 
this local species may be passed over. It differs from 
the immature C/V. ézdentata in being more slender, lighter 
in colour, having a deeper suture and being without any 
carination round the basal ridge, which carination is a 
marked characteristic of the young of that species. 
It is not, however, entirely confined to trees. Mr. J. 
R. B. Masefield once took me to a thriving colony en- 
sconced in a limestone wall on the top of Caldon Low 
(where there are no trees). We pulled down a great deal 
of wall in our search, but comforted our consciences by 
building it up again. The greenish form is very beautiful, 
It occurs very locally in colonies. It is ovo-viviparous. 
