Shells of Common Occurrence. 151 
repose it inclines it at an angle of 70. It derives 
its generic name from a shelly bone attached to 

57 

57. Zua lubrica (the Common Varnished Shell), Diller. 
58-59. Azeca tridens (the Glossy Trident Shell), Pulteney. 
the columellar teeth, and termed the clausiwm, from 
closing up the aperture when the animal has 
retired within its habitation. The next little group, 
Zua lubrica (common varnished shell), and Ag ca 
tridens (glossy trident shell), are parallel in character, 
only the Zua is toothless, the Azeca ovate and 
toothed in the mouth. Both inhabit close shady 
wood, moss, and under stones and decayed leaves. 
The one is not quite, the other about, a quarter of 
an inch in length. The next group comprises the 
needle agate shell (Achatina acicula), the shell of 
the common amber snail (Succinea putris), and two 
Physe or bubble shells (P. fontinalis and P. hyp- 
norum). ‘The firstis indeed minute, interesting, and 
extremely delicate, having six convolutions, though 
only a fifth of an inch in length; but, indeed, dead 
specimens found in old Saxon coffins are more 
frequent than living ones occurring amongst roots 
of grass and moss. Suwecinea is from succinwm, 
