Type species: Euborlasia elizabethae (McIntosh, 1874).
Diagnosis. Lineidae with pair of horizontal lateral cephalic slits; dark-colored, bulky body mottled with dark or pale dots and anterior tip paler; caudal cirrus absent; thick cutis separated from outer longitudinal muscle layer of body by thick layer of connective tissue; body wall musculature with diagonal musculature between outer longitudinal and middle circular muscle layers; nerve plexus wedged between two layers of diagonal musculature of body wall; proboscis with outer circular, diagonal, inner longitudinal, and inner circular muscle layers, with 0–2 muscle crosses (modified heterotype sensu Chernyshev 2015); vascular plexus present around foregut; neurocord and neurocord cells absent.
Remarks. Proboscis of Euborlasia gotoensis and E. proteres has outer longitudinal musculature, therefore these two species should be excluded from the genus Euborlasia. Euborlasia obscura (Friedrich, 1958) should also be excluded from the genus because it is distinguished by a caudal cirrus and a uniform body coloration (Friedrich 1958).