Horseshoe crabs are marine living fossils, probably traced back to 485 million years ago. There are two horseshoe crab species found in Hong Kong.
Horseshoe crabs are an ancient marine chelicerates, identified as the Class Merostomata, Order Xiphosura. The animals are identified by the possession of appendages around their ventral mouth and their swimming legs at their distal end. They have closer lineages with trilobites and arachnids such as spiders and scorpions instead of the "real" crabs which are crustaceans. Four extant species of horseshoe crabs are found and have survived over the geological period. They are classified to three genera in two families under the Superfamily Limulacea. They have hardly changed in millions of years. The oldest horseshoe crab fossils are probably traced back to the Cambrian period, which is nearly 485 million years ago. Therefore, the existing horseshoe crab species are treated as living fossils. …show more content…
Oriental Blechnum

Blechnum orientale is an evergreen fern forming a clump of arching fronds from 20 to 200cm tall, growing from a thick rhizome that rises to a short, erect trun. The plant is sometimes harvested from the wild for local use as a food and a medicine. It is often cultivated as an ornamental.
The plant is anthelmintic, antiviral, contraceptive and tonic. It is used in treating urinary complaints, impotence, boils in babies and older children and diarrhoea. It is believed that total sterility in women can be done by eating the new leaves of this plant each day for three complete days, then waiting a fortnight and repeating the treatment again.
A paste of the young fronds can be used to treat abscesses and fungal skin infections, esp ringworm, and to stop bleeding.The plant has components of essential oil, phenolic compounds and triterpenoids.

http://tropical.theferns.info/viewtropical.php?id=Blechnum%20orientale

3. Bamboo Pit