[1] Cycloxanthops novemdentatus is typically brown or red in color, but can also be purple.

[2] Immature individuals can be distinguished from adults by the width of the third and sixth abdominal segments, length of marginal abdominal hair, sparse layer of hair on the swimmerets, and the presence of a structure known as a "lock mechanism" on males.

[4] After individuals reach approximately 6.5 mm in carapace width, sexual dimorphism is apparent due to the different size and shape of abdominal segments.

[4] Cycloxanthops novemdentatus is the largest member of the family Xanthidae found in California.

[2] Cycloxanthops novemdentatus has been observed cracking open and feeding upon purple sea urchins.