The Dog Whelk (Nucella lapillus), also known as the Atlantic dogwinkle, is a species of predatory sea snail. It's shell is small and rounded with a pointed spire and a short, straight siphonal canal (a groove on the underside of the shell) and a deep anal canal. The overall shell shape varies quite widely according to the degree of exposure to wave action of the shore on which a particular population lives but the body whorl (the largest section of the shell where the majority of the visceral mass is located) is usually around 3/4 of the total length of the shell. The aperture is usually crenelated in mature dog whelks, less often in juveniles.
The shell surface can be fairly smooth interrupted only with growth lines, or when the snail is living in more sheltered areas the shell surface can be somewhat rough and lamellose. The surface is spirally corded. The outer lip is dentate and ridged within. The columella is smooth.
The external shell color is usually a whitish grey, but can be a wide variety of orange, yellow, brown, black, or banded with any combination of these colors. They can even, occasionally, be green, blue, or pink.