There is no hard-and-fast rule about the use of "cf." and other abbreviations. However, the following usages are very widespread in biologic circles, and are required by some paleontologic journals: Monfiloconchus pauli: The identification is certain. Monfiloconchus cf. pauli (or cf. M. pauli): The identification is uncertain because the material is fragmentary or otherwise flawed. Monfiloconchus aff. pauli (or aff. M. pauli): The material is good enough to identify, but may belong to an unnamed species related to M. pauli. Monfiloconchus pauli?: Definitely Monfiloconchus, but may not be pauli. Monfiloconchus? pauli: Definitely pauli, but this species may not belong to Monfiloconchus (for instance, the taxonomy of this genus may need revision.) ?Monfiloconchus pauli: Both genus and species are in doubt. You will occasionally see other abbreviations, especially in the older and more technical literature. Schenk and others (1948, Procedure in Taxonomy, p. 27-29) list three pages of Latin words and abbreviations, including the following, which I have modified slightly: aff. = affinis = having affinity with but not identical with auct. = auctorum = of authors [that is, of various authors] cf. = confer = to be compared to emend. = emendatio = emended f. = forma = form fide = trusting [the written word of] gen. et sp. nov. = genus [novum] et species nova = new genus and species ibid. = ibidem = the same [reference] incertae sedis = of uncertain position in litt. = in litteris = in correspondence lapsus calami = a slip of the pen loc. cit. = loco citato = [in the] place cited [to the page] mihi = [belonging] to me (i.e., my new species) nob. = nobis = [belonging] to us nom. nov. = nomen novum = new name nom. nud. = nomen nudum = nude name (new name given without an illustration or description) non = not nec = nor non vidi = I have not seen [it] non viso = not seen nov. = novum = new olim = formerly op. cit. = opere citato = [in the] work cited partim = part passim = here and there pro parte = in part q. v. = quod vide = which see s.l. = sensu lato = in a broad sense s.s. = sensu stricto = in the strict sense sic = thus; [this is] so (that is, exactly as shown) sp. = species = species (singular) spp. = species = species (plural) sp. nov. = species nova = new species subgen. = subgenus = subgenus supra cit. = supra citato = cited above teste = according to [the spoken word of] vide = see Schenk, Edward T., McMasters, John H., Keen, Myra A., and Muller, Siemon William, 1948, Procedure in taxonomy (2nd edition): Stanford, California, Stanford University Press, vii + 93 p. Also, an exclamation point (!) is occasionally used to indicate that the author has seen a particular specimen, not just read about it. Andrew K. Rindsberg Geological Survey of Alabama