C. Gallstones. Sizes
are variable. a. tetrathedron - rough sketch of several I saw in
the 1930s; b. subcrystalline
shape with rounded edges and corners; c. portion of globular
stone that exhibits
concretionary growth. (b
& c images retouched, etc.-- from advertisements for gallstones of
oxen on www.geocities.com
& www.ec21.com)