SALT AND FRESH-WATER CLAMS. zt 
apart, and then slipping the idols in between the mantle and 
the shell. After a lapse of time they collect the shells and 
open them, and adhering to the interior of the shells they 
find the little lead images coated with a layer of pearl; these 
are neatly cut out from the shell, and are worn as charms. 
It is a matter of wonder that some enterprising Yankee 
has not had recourse to this, as a novel mode in getting up 
shirt studs and sleeve buttons. 
All these shells increase in size by depositing lime around 
the margin of the shells, and the concentric lines upon the 
outside of these shells indicate successive periods of growth 
and repose. 
For additional information regarding another species of 
bivalve, the salt-water mussel, the reader is referred to Vol. 
II, p. 243, of this Magazine. 

EXPLANATION OF PLATE I. 
Fig. 1. preme. Mya arenaria, with the left valve removed. m, heart, 
Z5 
ntestine; G, gills; P, palpi; M, mouth; AN, anterior trans- 
verse muscle, a anterior adductor. Po, posterior 
adductor; F, pening in the mantle for foot; v, vent. 
O, 
hi re Muros the clam with its back uppermost, and 
the anterior end turned to the left. 
Fig. 2. gus in its natural position in the mud, head downward, 
the tubes extended to the surface of the mud. 
F, foot; v, ventricle; a, auricle; G, gills; antle; s, shell 
Fig. 4. Transverse section of — showing ew position of the spring to 
shell. M, muscle; L, ligam 
Fig. 5. Tini section of Tato, showing ie postion of the spring to 
, muscle; L, ligamen 
Fig. 6. Fresh-water clam, Unio complanatus, in its dii position, crawl- 
ing. The anterior end is depressed, and the foot is seen 
thrust out 
Fig. 7. Heart of clam seen from above. v,ventricle; aa, auricle; G G, line 
ills 
of gills. 
Fig. 8. Young of Unio. 

