  The low-temperature variation of the London penetration depth $\lambda (T)$
in the candidate topological superconductor Nb$_x$Bi$_2$Se$_3$ (x = 0.25) is
reported for several crystals. The measurements were carried out by means of a
tunnel-diode oscillator (TDO) technique in both field orientations ($H_{rf}
\parallel$ $c$ and $H_{rf} \parallel$ $ab$ planes). All samples exhibited power
law behavior at low temperatures ($\Delta\lambda\sim T^2$) clearly indicating
the presence of point nodes in the superconducting order parameter. The results
presented here are consistent with a nematic odd-parity spin-triplet $E_u$
pairing state in Nb$_x$Bi$_2$Se$_3$.
