The penpoint gunnel was first formally described in 1854 by the French biologist Charles Frédéric Girard with the type locality given as Presidio, San Francisco, California.

If there is no vegetation (in winter, for example), it can also inhabit rocky areas, lurking under rocks and in protective crevices.

It most easily distinguished by the dark bar below each eye, as it is commonly found peeking out of a kelp bed or crevice.

The first spine of the anal fin is large and grooved like a fountain pen point.

[5] This is an elongated fish which has long based low dorsal and anal fins.