The genome sequence of the Celtic sea slug, <i>Onchidella celtica</i> (Audouin & Milne-Edwards, 1832) (Systellommatophora: Onchidiidae)

We present a genome assembly from an individual <i>Onchidella celtica</i> (Celtic sea slug; Mollusca; Gastropoda; Systellommatophora; Onchidiidae). The genome sequence has a total length of 1 141.02 megabases. Most of the assembly (99.92%) is scaffolded into 18 chromosomal pseudomolecules. Gene annotation of this assembly on Ensembl identified 12 582 protein-coding genes. The mitochondrial genome has also been assembled, with a length of 13.99 kilobases. This assembly was generated as part of the Darwin Tree of Life project, which produces reference genomes for eukaryotic species found in Britain and Ireland.