  This work combines new observations of NIR starlight linear polarimetry with
previously simulated observations in order to constrain dynamo models of the
Galactic magnetic field. Polarimetric observations were obtained with the Mimir
instrument on the Perkins Telescope in Flagstaff, AZ, along a line of constant
Galactic longitude (\ell = 150\circ) with 17 pointings of the 10' \times 10'
field of view between -75\circ < b < 10\circ, with more frequent pointings
towards the Galactic midplane. A total of 10,962 stars were photometrically
measured and 1,116 had usable polarizations. The observed distribution of
polarization position angles with Galactic latitude and the cumulative
distribution function of the measured polarizations are compared to predicted
values. While the predictions lack the effects of turbulence and are therefore
idealized, this comparison allows significant rejection of A0-type magnetic
field models. S0 and disk-even halo-odd magnetic field geometries are also
rejected by the observations, but at lower significance. New predictions of
spiral-type, axisymmetric magnetic fields, when combined with these new NIR
observations, constrain the Galactic magnetic field spiral pitch angle to
-6\circ \pm 2\circ.
