principium: translated in the ed. pr. as "first point" but see OLD, s.v. 7b.
For oysters in Britain see Winder in Milne (1985), 91-5 and cf. Dannell and Wild (1987), 69, VRR III, 114. In the ed. pr. we suggested Cordonoui or Cordonouae as the nominative form of the place-name but it could also be Cordonouia (cf. Vinovia, 185.26 note). There is still no firm evidence for its location, but the Thames estuary on the north Kent coast would be a suitable area.
missit: see 255.i.6-8 note and the references there given.
Perhaps c]arissim[e rather than k]arissim[e, since we would be more likely to see some part of the bottom of a k, cf. ed. pr. The latter is adopted by CEL.
The evidence now available for the form in which addresses were written on the backs of the leaves makes it certain that is part of the identity of the sender, slanting upwards from left to right. The reading of i at the end seems quite secure; rather than an ablative of the type found in 311.back 4 (Sollemni), 312.back 4 (Tullioni), we may have the end of a genitive which will have followed the symbol for centuria or turma.