Species Versus Form
(Original Forum Question : Is Conus bocki a form of Conus sulcatus ? The book Shells of the Philippines says it is a separate distinc species (previously thought to be a form of sulcatus) but The Manual of the Living Conidae shows it as a form of Conus sulcatus. Which is correct ?)
There is really no way to definitively answer such a question. A taxonomic placement is not an absolute that can be precisely determined, like the formula of a chemical compound. Rather, it is the considered opinion of a taxonomist, based on his/her subjective interpretation of whatever objective evidence is available. Sometimes a given placement finds favor with the majority of authors. Other times one author interprets the evidence differently from another, or places greater weight on certain kinds of evidence than another, resulting in conflicting opinions regarding the proper placement. Since this is how all taxonomic assignments are made, and since there is no objective standard against which to measure such carefully considered opinions, one cannot dogmatically state that one opinion is "wrong" and the other is "right". We can consider the apparent relative expertise of the individuals offering such competing opinions, and decide which one inspires the greater level of confidence. Or we can state which opinion is currently accepted by the majority of experts; but that still is not an absolute indicator of "correct" vs. "incorrect".
(Answer by M. Paul Monfils via the Forum)