|Platypus by Frederick Nodder published in Naturalist's Miscellany 1799|
In 1798 the Governor of New South Wales John Hunter made possibly one of the first observations of the platypus by a European. He saw an Aborigine spearing 'a Small Amphibious Animal of the mole kind' in a lake near Sydney. He obtained this strange animal, preserved it in spirits and sent it back to England.
This sample reached Newcastle in 1799 and was recieved by Thomas Beswick. Beswick wrote in his General History of Quadrupeds (1800) that 'it appears to possess a three fold nature, that of a fish, a bird and a quadraped, and is related to nothing that we have hitherto seen.'
The naturalist Dr. George Shaw also obtained one and published an illustration of the animal by Frederick Nodder in the Naturalist’s Miscellany. According to Ann Moral in Platypus this was the first published depiction of the platypus.  Shaw gave the animal the name Platypus anatinus. This was from the Greek platypous meaning flat-footed and the Latin anatinus meaning duck-like. Although officially this name was later changed the term 'duck-billed platypus' stuck.
Shaw regarded the platypus specimen he had with suspicion. He wrote that:
...of all the Mammalia yet known itseems the most extraordinary in its conformation; exhibiting the perfect resemblanceof the beak of a Duck engrafted on the head of a quadraped… I almost doubted the testimony of my own eyes…
Hunter was not alone in his suspicions, other naturalists were doubtful and the surgeon Robert Knox also felt it was likely to be a Chinese creation. However, this did not stop people from trying to place the platypus in with the other classifications of animals. It was problematic as it seemed to stretch across several categories. It had a bill (like a duck), it layed eggs, yet also fed its young with milk.
Musing on how such a creature came to exist Hunter formed the theory that it was the result of ‘a promiscuous intercourse between the different sexes of all these different animals’. Gradually as more specimens arrived in Europe from Australia the suspicions about its origins were lifted and increasing focus was placed on trying to classify it. In 1803 Etienne Geoffrey St-Hilaire coined the term ‘monotrome’,meaning ‘one hole’ and placed both the platypus and echidna a class of his creation called ‘monotremata’. This was based on both animals having a single cloacalchamber. They are still in this category today.
 Moyal A, Platypus: The Extraordinary Story of How a Curious Creature Baffled the World, Allen & Unwin. 2002
 Anon, Duckbilled Platypus, museumofhoaxes.com, last checked on 08/07/2011
All quotes from Chapter 1 of: Moyal A, Platypus: The Extraordinary Story of How a Curious Creature Baffled the World, Allen & Unwin. 2002
For more infomration also see Ritvo H, The Platypus and the Mermaid: and Other Figments of the Classifying Imagination, Harvard University Press, 1997