Hi checking out Clara(Jessie) on the 1851 census and checking the other children suggests from the GRO Index that the Mothers maiden name was Tonkin.
Marriage Joseph Lendaryou to Elizabeth Tonkin Parish Kea 10th July 1830
Her sister Caroline Landeryou married Wiliam Edwin Lane 14th July 1860 Parish Chapel, St Pancras Father Joseph occ Carpenter
In 1851 census Caroline is 10 b Truro along with her other siblings and parents at Castle Place, St Pancras
Census Ref HO107/1498/191/38
On Anc**** the family have been transcribed as LINDERYN
I also could not locate a birth registration for either a Clara or Jessie c 1843 in Cornwall, but as the other children in St Pancras 1851 had mothers maiden name Tonkin , their is this one:-
Charity Landeryon Dec qtr 1843 Truro v9 page 329 mmn Tonkin
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