A special class of weighted
translation semigroups {St} on ℒ2(ℛ+) is studied. The weakly closed algebra 𝒜
generated by the semigroup is maximal abelian and the spectra of elements of 𝒜 are
studied. It is shown that each densely defined linear transformation commuting with
𝒜 is closable and that every transitive algebra containing 𝒜 is weakly dense in the
full algebra of operators on L2(ℛ+).