Possible spin-parity quantum numbers for excited charmed baryon resonances are discussed in this work. Our main results are: (i) Among the five newly observed $��_c$ states, we have identified $��_c(3090)$ and $��_c(3119)$ with radially excited $\frac12^+(2S)$ and $\frac32^+(2S)$ states, respectively, and $��_c(3000)$ with $\frac12^-(1P)$ and $S=\frac32$. The two states $��_c(3050)$ and $��_c(3066)$ form a $P$-wave $(\frac32^-,\frac52^-)$ doublet. (ii) The widths of $��_c(3066)$ and $��'_c(2930)$ are calculable within the framework of heavy hadron chiral perturbation theory. (iii) Since the width of $��_{c0}(\frac12^-)$ is of order 410 MeV, not all observed narrow $��_c$ baryons can be identified with $1P$ states. (iv) For the antitriplet $��_c$ and $��_c$ states, their Regge trajectories for the orbital excitations of $\frac12^-$ and $\frac32^-$ are parallel to each other. Based on this nice property of parallelism, we see that the highest state $��_c(2940)$ does not fit if its quantum numbers are $\frac32^-$ as found by LHCb. We suggest that $��_c(2940)^+$ is most likely the $\frac12^-(2P)$ state. (v) The charmed baryon $��_c(2800)$ cannot be a $\frac12^-$ state; otherwise, its width will be over 400~MeV, too large compared to the measured one. (vi) In the study of Regge trajectories of $��'_c$ states, we find a missing state. It should have quantum numbers $\frac52^-$ with a mass around 2920~MeV.

21 pages, 7 figures. Sec. II.A is substantially revised. Quantum number assignment to Omega_c(3050) and Omega_c(3066) is modified. Two more figures for the Regge trajectories in the (n_r, M^2) plane