Dear Patrick,
Below are George Radwin's descriptions of Anachis avara and A.
lafresnayi, from The Veliger, Vol. 20, No. 2:

Costoanachis avara (Say, 1822)

Shell moderate in size (10 - 20mm in length); spire
slightly greater than 1/2 shell length, whorls convex, suture
shallow; body whorl cylindrical, moderately broad, aperture
moderately wide, apertural lip slightly thickened, weakly denticulate
interiorly, columella straight, nondenticulate; siphonal canal short and
straight; sculpture of widely spaced ribs on body whorl only, all other
whorls
smooth. Color pattern of irregular brown blotches on a white background.


Costoanachis lafresnayi (Fischer & Bernardi, 1856)

Moderately large (10 - 16mm in length); spire high (more than 1/2 total
shell length),
whorls flat-sided, suture moderately impressed; body whorl fusoid;
aperture
moderately broad, apertural lip thickened; denticulate interiorly,
columella straight and
strongly denticulate, siphonal canal short to moderately long, slightly
bent; sculpture of
numerous prominent axial ribs crossed by weaker spiral grooves; color
from straw yellow
to chestnut brown with a spiral subsutural row of white spots.


Hope this helps.


- James