Family Spirobolidae Bollman 1893

Taxonomic Note: the following two specific names have been variously synonymized and split throughout the last century. Recently, it was suggested that they be referred to as " Narceus americanus / annularis complex" (Shelley et al. 2006). Both forms (whether they are a single species, two species, subspecies, or morphs) can be found in GSMNP; for convenience these are listed separately, but are considered to be one species in the summary.