The species differs from all other species of the genus in having fewer gillrakers on first arch (4 or 5 + 19-21 = 24 or 25 total vs. 8-14 + 20-29 = 28-42 total). In addition, it differs from other Atlantic species in having a ventral branch of obliquus dorsalis 3 muscle (vs. its absence in the other two species) and in having a posteriorly projecting extension of the cartilaginous lateral end of ceratobranchial 4 (vs. its absence in the other two species; S. berryi has a small accessory cartilage associated with the lateral end of ceratobranchial 4; the specimen of S. octoactinus examined may have had a very small accessory cartilage that was lost during dissection).