The shell was originally described by Smith, 1888 as Pleurotoma parilis (in latin):
Testa oblonga, subturrita, alba, inter costas prope sed infra suturara rufo maculata, ot supra costas punctorum ruforum seriebus spiralibus 2-3 (in anfr. ultimo 3-4) ornata; anfract. 7, supremi dúo laeves, convexi, caeteri paululum convexi, inferne leviter angustiores quam supra, costis subobliquis 9-10 (in anfr. ultimo ad basim attingentibus) instructi, ubique tenuissime densequo spiraliter striati; apertura angusta, longit. totius ½ vix sequans; labrum incrassatum, superne semicirculariter sinuatum; canalis brevis, angustus.
Long. 7.5 mm.; diam. 2.66 mm.

Keen (1971) gives another description of P. parilis, which was renamed by Dall to Agatothoma alcippe:
The whitish shell is variously banded with narrow or broad bands of brown, axial ribs tending to be continuous, the shoulder strongly tabulate, spiral striae fine and even. Mature specimens from 5 to 11 mm in height; diameter, 2.5 to 5 mm; larger specimens showing thickened varices that represent earlier resting stages.

Dall (1919) described C. euryclea, which is considered as a synonym of A. alcippe:
Shell minute, whitish or pale brownish, subcylindric, turrited, the nucleus with a projecting minute subglobular apex and about one and a half smooth whorls followed by about four and a half sculptured whorls; spiral sculpture of minute close-set threads covering uniformly the whole surface; suture distinct, appressed, the whorls shouldered immediately in front of it; axial sculpture of (on the last, whorl seven or eight) prominent, slightly protractively oblique ribs, with wider interspaces, extending over the whole whorl and prominent at the shoulder, but not continuous over the spire; aperture narrow, outer lip varicose, thick, striated in front, smooth within, the anal sulcus conspicuous but not deep; inner lip smooth, the canal hardly differentiated. Height of shell 5mm.; of last whorl, 3.5 mm.; diameter, 1.75 mm.

Dall (1919) described C. pyrrhula, which is also considered as a synonym of A. alcippe:
Shell small, brownish with a white peripheral band, brilliantly polished: with a pointed nucleus of two smooth rounded and one peripherally sharply keeled whorls; and about six subsequent whorls; suture distinct, appressed, fasciole constricted; spiral sculpture of about a dozen grooves with wider interspaces on the base and canal; axial sculpture of (on the last whorl 13) narrow sigmoid ribs extending from the fasciole to the canal with somewhat wider smooth interspaces; aperture contracted, anal sulcus large, with flaring margin and subsutural callus; outer lip sharp edged, infolded, a prominent varix behind it and under the varix internally a thickened ridge with about five short oblique lirae; inner lip erased; pillar longer with about six lirae; canal short, deep, moderately recurved. Height of shell, 11mm.; of last whorl. 6.5 mm.; diameter, 5 mm

Head of the Gulf of California to Santa Elena Peninsula, Ecuador, at low tide and to depths of 20 m in gravel near rocks