As defined by Vink this species ranges from North Carolina around the peninsula of Florida and then along the Gulf Coast of the United States to Yucatan. This is a most unusual geographic distribution. However, Vink's Figs. 12a and 12b are essentially identical looking and look very much like the specimens from the scallop trawls of the eastern United States. If Gradiconus sennottorum and G. largillierti are different species then they are sympatric in Yucatan. Adults of G. largillierti are less turnip shaped than are the type specimens of G. sennottorum. However, all G. sennottorum are not as turnip shaped as is the type specimen. This brings up another point, young specimens of G. largillierti are often much more turnip shaped than larger ones. I think it is important to note that shell shape is variable in Gradiconus largillierti and G. sennottorum as well as among all the other southern Gradiconus recently described as new species. This means that shell coloration or ornamentation is the only shell trait left to use to separate taxa. Shells identified as G. sennottorum are often lightly colored but they occur along side G. largillierti that can be equal in shell shape but only have color patterns that are better developed. When large samples are available from trawls in the Yucatan area, I think that G. largillierti and G. sennottorum will prove to be conspecific.