Was there ever a hypothesis about a planet called Biga? I just re-read a popular astronomy book that was published when I was a child, about 1973. It starts with an interview to Harold C. Urey where the interviewer asks about a hypothetical planet in our solar system called Biga.

Has a hypothetical planet ever been called "Biga" by its  proponents, in the same way there was a proposed planet "Vulcan", or is this "Biga" name a printing or translation error?

If it's a mistake and there never was a "Biga" proposal, which is the proposed planet with the most similar name?

This link contains such interview, in Spanish. I will translate and quote its most relevant text:


  Interviewer: At present, do we know all the planets of the Solar
  System, or is there the possibility of still unknown planets in our
  system?
  
  H.C. Urey: We certainly know the nine usual planets. Recently there
  has been much talk of another object moving in space and supposed to
  be close to the Solar System, but I am not sure that it is a real
  hypothesis, and personally I think it is better to wait before
  deciding whether it is Not of a planet. I consider it sufficient to
  say that there are Mercury, Venus, Earth, Mars, Jupiter, Saturn,
  Uranus, Neptune, Pluto and the asteroidal belt.
  
  Interviewer: When talking about this object, are you referring to the
  so-called planet Biga?
  
  H.C. Urey: Yes, that's what I meant, but I'm not sure of its
  existence.


Please, remember:

1- This interview mas made about 45 yeras ago. 

2- I'm not asking if this hypothesis is correct or even possible. Only want to know more about this hypothesis which was well known by H. C. Urey in the 70's.

3- I'm not asking if the name "Biga" is a correct proposal of a name for a planet in our Solar System accordind to current naming rules.
If another planet in our solar system was to be named, I think that Biga wouldn't be the first name to come up, all of the known planets in our solar system are named after Roman deities and Biga is not a deity but rather a cart on which mostly Luna is depicted. I have never heard of this proposal and if the 'rules' are used for naming, it wouldn't be the first candidate.