48 COLLINGE : BURROWING HABITS OF CERTAIN MOLLUSCS. 
Pupa umbilicata Drap. Often found beneath the bark of old 
trees also in the ground at a depth of five or six inches. 
Balea perversa lL. In dry weather this species burrows to a 
depth of from six to eight inches; it is also found under large 
stones and beneath the bark of trees 
Clausilia rugosa Drap. Frequently under large stones, but I have 
never met with it below the surface. 
ore elegans Miill. During the summer I have met with 
s shell three and four inches below the surface. 
- corneum L. I have collected this species in thick 
and sometimes hard mud at depths varying from three to 
fourteen inches at all seasons of the year. 
Sphzrium rivicola Leach. Generally buried in five or six inches 
of fine mud. Have met with it once in winter in hard mud 
four inches deep. 
— lacustre Miill. Burrows to great depths ; often found 
n and fourteen inches below the surface in dry ponds. Have 
not met with it during the winter months. Dr. Jeffreys states 
that he ‘found it alive in the hardened mud of a pond which had 
been drained and its bed so completely dried up by the sun as 
scarcely to show the marks of any footsteps on it.’ 
Pisidium Pfr. With the exception of P. voseum Scholtz, I have 
met with all the Pisidia at depths varying from four to twelve 
inches, and at various seasons of the year. 
Unio Phil. The members of this genus are often covered with 
a layer of fine mud four to six inches thick. I have not met 
with any actual cases of burrowing, nor have I found them in 
hard mud. 
Anodonta Cuvier. According to M. Drouet, the Avedonte usually 
hybernate before the close of autumn, when they bury them- 
selves deep into the mud, remaining there until the middle of 
spring. Mr. Rhodes mentions that a variety of 4. cyguea at 
Pudsey (Yorks.), in a disused mill reservoir, is found buried at 
a depth from eight to twelve inches in winter, and two to four 
inches in summer, but always imbedded. 
Paludina contecta Miill. In Yorkshire I have found this species 
in the summer in thick mud quite ten inches deep; in the 
River Cherwell, in the north of Oxfordshire, I have brought up 
specimens in my net as deep as fourteen inches. 
Paludina vivipara 1. In fine mud, a few inches deep, I have 
often met with this species. 
Silas eyte 
Naturalist. 
