Definitions of Circumscribing and Excising for Coronoids

A coronoid is said to be circumscribed if its associated benzenoid is circumscribed. Hence the following definition may be formulated (cf. Cyvin SJ, Brunvoll and Cyvin 1991b Brunvoll, Cyvin BN and Cyvin 1993b also John 1990). 

In other words, the added hexagons constitute a primitive single coronoid. The circumscribed coronoid C is designated 

An excised coronoid is defined in connection with excising, a process opposite to drcumsciibing. The strict definition, which is formulated below, is an adaptation of the definition of an excised benzenoid by John (1990). 

DeJmitUm S.t The coronoid C is excised by removing all the vertices on the outer perimeter of C and all their incident edges. 

---