A common jingle is rosa mundi sine spina, but I have long been intrigued as to the origin of the supplementary expression 'fish without spine'. Is there any mediaeval or other origin for this latter expression? I first came across it in David Selborne's play 'Alison Mary Fagan' (written for the daughter of musicologist Roger Fiske). I have not been able to source any 'piscis sine spina' - is this merely an attempt at a joke? [The play has AMF reciting: rose without thorn, fish without spine'...]