  We present the results of our new study of known RR Lyrae variable stars. All
observations available for these stars in the Catalina Surveys were analyzed,
and double-mode variations were identified. We studied the Petersen diagram and
period distribution for the double-mode RR Lyrae variables in the Galactic
field, pulsating in the first-overtone and fundamental modes. The double-peaked
character of the period distribution was detected for Galactic RR(B) stars,
corresponding to Oosterhoff's classes of globular clusters, which indicates
that the age and evolution stage of RR(B) stars in the field and RR Lyrae
variables in globular clusters are probably the same. Besides, we discovered
five RRC stars with two simultaneously excited non-radial pulsations
(equidistant triplets).
