These are actually all quahogs!
The quahog (pronounced coe-hog) is a species of hard-shelled clam and the one we most commonly enjoy in our chowders and po boys. All those other names - from little neck on up - are this same species of clam and just refer to how large the clam has grown.
Little Neck: The smallest size of clam, amounting to 7-10 clams per pound.
Cherry Stone: A little larger, you'll get 6-10 cherry stone clams per pound.
Top Neck: These are sometimes also labeled as count neck clams, and they equal roughly 4 clams per pound.
Quahog: These big guys are also called chowder clams and weigh in at a mighty 2-3 clams per pound.
Which type of clam to buy depends on how you want to prepare them. The clams get tougher and chewier as they get larger, making these sizes ideal for chowders, stuffing, frying, and other cooked preparations. Choose smaller sizes when quickly steaming, grilling, or eating raw.
What's your favorite way to enjoy clams?
Related: How to Clean the Sand out of Clams