  I formulate the theory of three dimensional "Malthusian flocks" -- i.e.,
coherently moving collections of self-propelled entities (such as living
creatures) which are being "born" and "dying" during their motion -- whose
constituents all have a preference for having their velocity vectors lie
parallel to the same two-dimensional plane. I determine the universal scaling
exponents characterizing such systems exactly, finding that the dynamical
exponent $z=3/2$, the "anisotropy" exponent $\zeta=3/4$, and the "roughness"
exponent $\chi=-1/2$. I also give the scaling laws implied by these exponents.
