In the vicinity of Grand Isle, Louisiana, Menticirrhus americanus, a marine fish of the surmullet family, carries in the intestine an acanthocephalan which has been previously undescribed. The attention of the writers was first called to this species by collections made available by Mr J. E. Tobie. Additional specimens were later secured from Dr H. J. Bennett. This new species is clearly a representative of the family Rhadinorhynchidae but in it are embodied peculiarities and combinations of characters which preclude its inclusion in any previously recognized genus. Hence a new genus is herein proposed and the species is described as Illiosentis furcatus.