Large reddish brown terrestrial leech. Found in peat in a penguin rookery on Snares main island. 7-9cm long extended, 2-3cm wide (possibly just fed). Round sucker on under surface. Papillae, red-brown with yellow colouration. Coolest thing I have ever seen.
Everybody knows that there are many bloodsuckers in all the ponds and creeks. So do I. And I have neoprene socks. But I was to lazy to wear them...
Arion ater or Arion rufus, that is the question. I'm leaning toward ater, not wishing to resort to disection to verify.