A Port Jackson shark's egg case. The screw-like helical flanges help the mother shark to secure the egg within rock crevices.

Mermaid's purses are the normally empty egg cases of dogfish, skates and rays. They are among the objects which are washed in by the sea, and can be found at the strandline, which is the furthest point of the highest tide. Download high resolution version (2048x1536, 627 KB)Egg case of Port Jackson shark. ... Download high resolution version (2048x1536, 627 KB)Egg case of Port Jackson shark. ... Screws come in a variety of shapes and sizes for different purposes. ... An average Whooping Crane egg is 102 mm long, and weighs 208 grams A baby tortoise emerges from a reptile egg. ... Spiny Dogfish, Squalus acanthias The name dogfish is applied to a number of small sharks found in the northeast Atlantic, Pacific, and Mediterranean, especially those in the three families Scyliorhinidae, Dalatiidae and Squalidae. ... Orders Batoidea - common rays and skates Myliobatiformes - eagle rays, manta rays Pristiformes - sawfishes Torpediniformes - electric rays Rays are a group (superorder Rajomorphii or Batoidea) of cartilaginous fishes. ...

The size of Mermaid's purses vary. Those of the lesser dogfish (Scyliorhinus caniculus) are around 5 cm long, while those of the greater dogfish (S. stellaris) are around 10 cm. That excludes the four long tendrils found in each corner, which assist in anchorage. Mermaid's purses from rays vary in that they have points rather than tendrils. The colour and shape of mermaid's purses also varies greatly from species to species. In botany, a tendril is a specialized stem, leaf or petiole with a threadlike shape that is used by climbing plants for support and attachment, generally by twining around whatever it touches. ...

The young fish would normally gestate between 6-12 months, but can be much longer for deep sea catsharks which lay their eggs in very cold water.