Shark

• Oviparity
Some species are oviparous like most other fish, laying their eggs in the water. In most oviparous shark species, an egg case with the consistency of leather protects the developing embryo(s). These cases may be corkscrewed into crevices for protection. Once empty, the egg case is known as the mermaid's purse, and can wash up on shore. Oviparous sharks include the horn shark, catshark, Port Jackson shark, and swellshark.
• Viviparity
Finally some sharks maintain a placental link to the developing young, this method is called viviparity. This is more analogous to mammalian gestation than that of other fishes. The young are born alive and fully functional. Hammerheads, the requiem sharks (such as the bull and blue sharks), and smoothhounds are viviparous.