The rhytina belonged to the same mammalian Order as the manatee of Florida and South America, and the dugong of Australia.
"Our Vanishing Wild Life" by William T. Hornaday
The death-year of the Rhytina race must therefore be altered at least to 1854.
"The Voyage of the Vega round Asia and Europe, Volume I and Volume II" by A.E. Nordenskieold
The rhytina, the Californian elephant seal, the great auk, and the Labrador duck have already been exterminated.
"Taxidermy and Zoological Collecting" by William T. Hornaday