The shell had formed a tube that let the air out; it took about thirty seconds, with diminishing intensity as the pressure dropped.

The white, minute shell forms a depressed sphere which is equally raised above and below.

Then the female, whose new shell has now formed, leaves, and another moves in.

The rate at which these shells form is greatly influenced by physical and chemical characteristics of the water in which these organisms live.

It seemed, too, as if a protective shell had formed about Rufo, a dark lining to battle the burning sunlight.

Some species septate; their embryonic shell, which is retained, forms a small, sometimes spherical, chamber.

Myriad tiny shells formed a long low hump, and he realized that early-rising collectors could appear at any moment.

The shell forms an open spiral with the later whorls separate.

Over time, the shells have formed a limestone that is known as Coquina.

The expanding shell of gas forms a supernova remnant, a special diffuse nebula.