Of the thousands who boat on the Thames during the summer few know or notice the beauty of the river shells. They are among the most delicate objects of natural ornament and design in this country. Exquisite pattern, graceful shapes, and in some cases lovely tints of colour adorn them. Nature has for once relaxed in their favour her rigid rules, by which she turns out things of this kind not only alike in shape, but with identical colour and ornament. Among humming-birds, for instance, each bird is like the other, literally to a feather.