Abstract
The strong-C N stars (including the SMR stars) and the R-type carbon stars are similar in that they occupy nearly the same part of the H-R diagram, in that their distribution in the medium-thick disk is similar, and in having about the same proportion of binary systems as are found in ordinary G and K giants. The spectra of both groups are alike in lacking enhancement of the s-process elements. The major difference between them is that at least most of the strong-C N stars are metal rich, while the R stars have nearly solar abundances of the common metals. This suggests the possibility that a few of the strong-C N stars are not SMR stars, but may be marginal R stars.
