  The cold molecular gas in the circumnuclear disk (CND) of radio galaxies
provides critical information for understanding the mass accretion onto active
galactic nuclei. We present the first detection and maps of HCN J=1-0 and HCO+
J=1-0 emission lines from the circumnuclear region of a nearby radio galaxy,
NGC 4261, using the Northern Extended Millimeter Array. Both molecular lines
are detected at a radial velocity of +-700 km/s relative to the systemic
velocity of the galaxy, and they arise from a CND with an outer radius of 100
pc. The velocity fields of HCN and HCO+ are fitted with a Keplerian disk
rotation. The enclosed mass is (1.6+-0.1)x10^9 M_solar, assuming a disk
inclination angle of 64 degree. The continuum image at 80 GHz reveals a weak
two-sided jet structure extending over 5 kpc along the east-west direction and
a bright core at the centre. The continuum spectrum between 80 and 230 GHz
shows a spectral index of -0.34+-0.02, which suggests optically thin
synchrotron radiation. The dense gas mass associated with the CND is calculated
to be 6.03x10^7 M_solar. It supports a positive correlation between the dense
gas mass in the CND and the accretion rate onto the supermassive black hole,
though there are uncertainties in the parameters of the correlation.
