Shell oval, moderately convex, solid, radiately strongly ridged. Sculpture consisting of strong radiating nodulose or spinose ridges, often interrupted by periods of rest ; interstices with more or less numerous radiate striae ; growth-lines prominent, and lamellar on the anterior part of the shell. Colour whitish, yellowish, or brownish, often chestnut-raved ; interior often blotched or raved with brown or purple ; basal plate white. Epidermis very thin, horny, deciduous. Protoconch minute, oblique, of 1 smooth and flatly convex whorl, mostly with a few brown lines ; the nepionic shell has very line concentric growth-lines, but no radiate sculpture. The shell is flatly to highly convex, with the apex lateral, posterior, and terminal. Interior porcellanous, polished, the margin of the roof more or less denticulate. Basal plate flat or convex, free margin sharp, almost straight ; length of the plate somewhat over one-third of the total length of the shell.
Length, 50 mm. ; breadth, 31 mm. ; height, 18 mm. (large specimen).
Dentition.—Hutton, T.N.Z.L, xv, 122, pl. 14, f. A.
Type in the British Museum.
Hab.—North Island of New Zealand. Brought to England by Captain Cook.
Remarks.—Sowerby's species was first figured, and his specific name has to be adopted. This again is a cosmopolitan species. Gray (P.Z.S., 1867, 737) mentions the following species as synonyms : C. echinus and hystrix, Broderip ; C. californica, Nuttall.
Fossil.-—Miocene and Pliocene.