Arthur Ransome Wiki

Pterodactyl is large, fast, sea-going powerboat used as a headquarters on his expeditions by the egg collector, Mr Jemmerling in Great Northern? Initially the others call it Dick's boat, as Dick would like to use a vessel of his own, big enough to live in, as a travelling observation post. With a boat like that, you could migrate with the birds (GN1).

The sailor from Pterodactyl is one of the servants of Mr Jemmerling on the Pterodactyl. He has Pterodactyl in red letters on his blue jersey (GN9). He follows the decoys up the valley (GN20), and at the end Mr Jemmerling and the sailor find and hide the eggs (GN27). The sailor grabs the gun and swings it towards Angus‘s dogs (GN28).

The sailor is the only crew member mentioned, except for Mr Jemmerling's visit to the Sea Bear (GN10):

A boat in davits was being swung over the side of the white motor boat. Two men were at the falls, lowering the boat to the water .... A man slipped down into the boat, cast off the tackles, and brought the boat to the ladder, where the owner of the Pterodactyl was waiting.