Diagnosis: Shell, minute, oval-conic with apex, broadly conic. Mature whorls, 4, slightly convex; suture, channelled and beaded. Sculpture of broadly, shallowly granular spirals with interspace, narrow; 4-5 spirals on the penultimate whorl. Aperture, subcircular, moderately angled above and outer lip, thin. Color, pale white with a few reddish brown spots on shoulder. It distinguishes from Onoba isolata (Kay) as (a) this shell has broadly granular spirals while Onoba isolata (Kay) has narrower spirals with broader interspace, and (b) the spire whorls of this shell are flatly convex while Kay’s shell is convex.
Distribution: Gould’s specimen was taken from the stomach of a haddock at Casco Bay. It is also found as beach drift at Lutao, Taiwan.
Dimension: 2.0 x 1.1 mm.
Remarks: Onoba sp. been reported in Chang (1998). This is a new record in Taiwan.
Reference for Identification: Gould (1870), p.301, Fig. 570.

Numerous sculptured rissoid species have been described from the North Pacific and Alaska. Some of these closely resemble Onoba mighelsi and /or Alvania torelli. I take this opportunity to give a brief review of those most similar to O. mighelsi /A. torelli:
• Alvania dalli (BARTSCH, 1927) described from Shuyak Strait, Afognak Island, Alaska, resembles A. mighelsi and A. torelli, especially the latter species but can be recognised by its sharply and finely striated protoconch with a sculpture visible under a stereomicroscopc at 50x.
• Alvania aurivilli (DALL, 1887) is larger, about 4 mm and has some line axial riblets in the interspaces between the spiral ribs. Its protoconch has a sculpture similar to Alvania bakeri and O. torelli, but much finer.
• Alvania castanella (DALL, 1887) is quite similar to O. mighelsi, and even more so compared with O. torelli. The holotype is not in good condilion and its protoconch sculpture can not be figured. It differs from A. mighelsi by having a much sharper sculpture on the teleoconch and no trace of axial sculpture. It differs from O. torelli by having more convex whorls, deeper suture, and a taller aperture.
• Alvania bakeri (BARTSCH, 1910) from Port Graham, Alaska, has a protoconch sculpture identical with that of O. torelli, but the shape of the teleoconch is quite different, smaller and with fewer and more convex whorls and a stunted shape. Nevertheless this is the North Pacific species most similar to O. torelli and I can not exclude the possibility that they are conspccific. The absence of material to show its variation and to follow its distribution has led me to regard them as distinct species.
• Alvania alaskana (DALL, 1887) is very similar to O. mighelsi. The holotype has no sculpture left on the protoconch and I figure a better specimen from Alaska, Ellington Island, which has a protoconch microsculpture identical with that of A. mighelsi. I can therefore see no reason to distinguish between them.
• Alvania dinora. The holotype is not in good condition and the protoconch sculpture is worn off. The type, however, is so similar to O. mighelsi, so I do not hesitate to synonymise it.

Point Barrow; and (Thorson, 1944) Grinnell Land and Newfoundland to Cape Cod, eastern and western Greenland; northern and eastern Iceland, Spitsbergen, and northern Norway. C. castanea (= Onoba mighelsii) has not been reported from the western Arctic.