  Particle lateral distributions were investigated in cosmic ray air showers
with energy $E_0 \simeq 10^{18}$ eV registered at the Yakutsk array with
surface and underground scintillation detectors with $\simeq 1 \times
\sec\theta$~GeV threshold during the period of continuous observations from
1986 to 2016. The analysis covers events with arrival direction zenith angles
$\theta \le 60^{\circ}$ within five intervals with step $\Delta\cos\theta =
0.1$. Experimental values were compared to simulation results obtained with the
use of CORSIKA code within the framework of QGSJet01 hadron interaction model.
The whole dataset points at probable cosmic ray composition which is close to
protons.
