Complex sentence: The outer subbasal transverse line broadens at the costa, and is outwardly margined by pale spots in the interspaces; these are anteriorly white and well defined, and posteriorly obscure or often absent.
Split into simpler sentences: The outer subbasal transverse line broadens at the costa, and is outwardly margined by pale spots in the interspaces. These are anteriorly white and well defined, and posteriorly obscure or often absent.