II looked at the photo by Dr.Adams that was provided here. I cannot see how anyone can seriously use this photo to ID theses closely related species. The photo is not that good, especially compared with Jim Vargo's photos.
The photo from CBIF shows a clear example of C. sensilis and is labled C. seniblis. If I had this specimen mounted on an imsect pin, I would be placing it in with my other C. seniblis specimens.
Robin McLean is correct about the flight dates of these two species. I do not expect to find C. sensilis until October in Florida. I do find all my examples of C. palliatricula earlier in the collecting season. So, perhaps, a specimen of C. sensilis emerged early.
I agree with Robin that much more research is needed with this genus, Chytonix, since there is four species listed in USA.

as the C. sensilis shown along with palliatricula at CBIF, but there's an equally dark palliatricula by James Adams here, and I can't find any reliable difference between the "iaspis" form of palliatricula and the 3 Jim Vargo specimens of sensilis shown at MPG.

The early date seems to favor palliatricula. Covell gives dates of June to August for that species, Handfield gives early and late dates of 27 May and 6 August in Quebec, and the Lepidopterists Society gives two dates in Oklahoma of 23 April and 9 August.

By contrast, the dates for sensilis are later: Handfield gives 1-31 July in Quebec, the Lep. Soc. gives an early date of 21 July in Massachusetts, to a late date of 13 October in Georgia, and a PDF doc by Wagner et al gives a flight season of "August in Connecticut, September in North Carolina, October in Florida". Generally, earlier than July would favor palliatricula, and later than August would favor sensilis.

Patrick, Dr. covell should have mentioned under Chytonix palliatricula that there is Chytonix sensilis (9557), which you have an excellent foto.