What is the English name of these sea snails?
Ốc bông = tiger moon snail (hotdeal.vn, Google images) or in Latin: Notocochlis tigrina (Wikipedia)

Ốc tỏi = Japanese bonnet snail (Facebook, Wild Fact Sheets, images, more images) or in Latin: Semicassis bisulcata (Wikipedia). Ốc tỏi is sometimes refered to as "garlic snail" (Hong Hai, Cooky), but this is obviously different from garlic glass snail, which is a land snail (Wikipedia).

Here on Facebook are Vietnamese/English translations for more than 100 types of seafood, including Ốc bông and Ốc tỏi.