part of part of zone of bone organ entotympanic bone pars endotympanica UBERON:0018655 This is present in the cat and forms the large medial part of the Bulla tympanica. It is not to be regarded as a part of the pars tympanica, which ossifies directly from connective tissue, whereas the Pars endotympanica is preformed in cartilage. The Septum bullae in the cat is formed by the Pars tympanica as well as by the Pars endotympanica(NOMINA ANATOMICA VETERINARIA (2005)).