The Murphy operators in the Hecke algebra Hn of type A are explicit commuting
elements, whose symmetric functions are central in Hn. In [Skein theory and the
Murphy operators, J. Knot Theory Ramif. 11 (2002) 475–492] I defined geometrically
a homomorphism from the Homfly skein C of the annulus to the centre of each
algebra Hn, and found an element Pm in C, independent of n, whose image,
up to an explicit linear combination with the identity of Hn, is the mth
power sum of the Murphy operators. The aim of this paper is to give simple
geometric representatives for the elements Pm, and to discuss their role in a
similar construction for central elements of an extended family of algebras
Hn,p.