The shell in non-crowded specimens of Chamaesipho brunnea is usually low conic, brown with prominent growth ridges basally, corroded upper sections are whiter and smoother.

Shell wall in juveniles, to 4 mm maximum diameter consists of six plates, which then reduce to four by fusion of carinolaterals with rostrolatera.

[1]: 322 The scutum is wider than high, and distinguished by its comparatively large, rectangular articular ridge.

Scutal adductor ridge, a character of the genus, is nearly absent, or poorly expressed.

[1]: 322, 323 [2]: 68 Diagnostic soft part features include a dark brown body with black cirri, and mandible with three, sometimes four teeth.

[6]: 58  As this species breeds primarily in spring and summer, water temperatures may be controlling factor in distribution.