The following genes with an identifier have been found but that do not have a mapping to Ensembl: 2
http://classic.wikipathways.org/instance/WP367_r135390 ced-13 with datasource WormBase
http://classic.wikipathways.org/instance/WP367_r135390 egl-38 with datasource WormBase
More details at https://www.wikipathways.org/WikiPathwaysCurator/GeneTests/genesWithoutEnsemblMapping