Blazon

Shield: Gules, on a chevron argent three trefoils slipped of the field.

Crest: A stag's head couped Proper.

Motto: Craignez honté (Dread shame).

Lewis Weston (and others?) quartered the arms : 1 - Dillwyn, 2 : Or an eagle displayed Sable(?), 3 : Argent, a chevron Azure between three ravens Sable and on a canton Sable a pheon Argent (Traherne), 4 : Either Dillwyn (repeated), or Argent a lion rampant between three crescents Gules, overall a pale Azure. (Dillon). The use of the Dillon arms was erroneous, and, in any case, they should have a fess overall not a pale.

Gallery
The Dillwyn arms in Swansea Guildhall.
Lewis Weston Dillwyn impaling his wife, Mary Adams (Llewelyn)
(Copied from the arms in Singleton Abbey, Swansea University)
Lewis Weston Dillwyn's bookplate, with the Dillon arms in the fourth quarter.